No, it is not a good idea, because exchangers generally only show the movement changes of the last 24 hours. You should use also an app like blockfolio or visit coinmarketcap.com to see at least the last three months. As I was new to day trading, I trapped into those + and - percentages with quite big loss, because I baught the cryptos on the highest points, compared to the last 7 days.

You can buy them maybe on Kraken. They provide USD/USDT trading pairs and if I understand right, they are also provided on exchange section, not only on margin trading.
https://blog.kraken.com/post/206/kraken-announces-support-for-crypto-dollar/
But to be sure, simply ask their support. They are fast in answering for my experience.
But they only seem to accept Bank transfers via third party
https://support.kraken.com/hc/en-us/articles/115000302327-Credit-Cards-Debit-Cards-PayPal-and-similar
But here is a thread with same question. On the last site you can see some interesting advices.
https://bitcointalk.org/index.php?topic=1540090.60

In my opinion the best multicoin wallet is Coinomi, because it is easy to use and also stores Ethereum tokens (but to get them listed, the ETH wallet must be exported to myetherwallet.
But it is an Android wallet and can't be used on PC.
For basics about wallets generally, I would recommend this thread:

https://bitcointalk.org/index.php?topic=1631151.0
It is about Bitcoin wallets, but will give you a good knowledge, how to find the best wallets, which will fit your needs.

There are several ways to purchase cryptocurrencies, depending on your country/region.
Preposter already suggested a few and I would add green trusted members here in Bitcointalkforum, ask also on local boards, there are several meetings of Bicoiners, Bitpanda and ATM for example in Austria, Switzerland and Poland.
But I wouldn't recommend Bittrex as safe exchanger. They set withdraw minimum to zero without warning and freeze funds. I would call that theft and the opposite of a secure exchanger, if they didn't refund their customers without ID verification.

It is the same like on your blog or app. You have several opportunities to get followers to your channel.
1. Get genuine followers with a meaningful headline.
2. Use paid services to do the promotion for you.
3. Paid services for paid followers (not reccommended, because they mostly are inactive)
4. Write articles on your blog, social channels and landingpages.
5. Cross promotion through existing channels.
6. Advertise here in forum.
Because of the many opportunities to get followers, you can not generally say, if all followers are real or not.
If you are providing here your telegram group with meaningful content or service, you needn't buy followers. It is only important to make it public and you are here (service section) on a good place, if your trlegram channel is about cryptocurrencies.

This also happened to me, as I was still not familiar with altcoins. I trapped at yobit into the issue with a shitcoin, because it was listed on investbox with high interests, but I couldn't sell it.
There may be a chance to sell your coin (with loss, but you wouldn't loose your whole amount). There are a few markets, where coins can traded also for dogecoin, litecoin and more.
Have a look at coinmarketcap.com and search for your coin. Click on "Markets" and you will see, where else you can sell your coin.

It would be enough to trade each day with 2% or 3% profit. (daytrading), but it is high risk.
Let us make a theoretical experiment.
• Go to Cryptopia or any other legit exchanger. The best, I think, is cryptopia for beginners.
• Deposit only 10$ (not more) in Bitcoin or altcoin.
• Study the cryptocurrencies
  ▪ Charts and historical data on coinmarketcap or blockfolio
  ▪ Read the coin info page on Cryptopia
  ▪ If you found interesting coins, look also here for infos
• Find out at least three coins, that are swinging since several weeks between certain price highs and downs.
• Buy and sell three different cryptocurrencies and go with the swings (the most difficult part, its like betting)
When you are able to gain profit of 3% each day, you will earn with your 10$
after month 1: 24,27$
after month 2: 58,92$
after month 3:143,00$
after month 4: 347,11$
after month 5: 842,53$
after month 6: 2.045,03$
after month 7: 4.963,83$
after month 8: 12.048,53$
after month 9: 29.244,94$
after month 10: 70.985,13$
after month 11: 172.299,55$
after month 12: 418.216,24$

For the case, you will not reach the target, blog your experiences on trading or write articles, when you have learned enough about cryptocurrencies and trading. Also trading journals are high visited.

Funny, that you mention Ardor in this context. I baught them a few days ago for around 0.0001100 and 0.0001000 BTC and now they are stable on 0.000081 BTC.
Back to the question:
I invested into an ICO and would take it as first decision, with a real and established company and a meaningful reference behind it. Projects, that combine traditional services with innovative network and database (blockchain) will be our future and I don't know, if I would get again the opportunity to be part of it with a little investment.
But I wouldn't invest my whole money into one coin, so I have a portfolio with several coins like Ethereum, tokens, Dogecoim and of course Bitcoin.

Deposit problems on Poloniex are mostly caused by slow networks of cryptocurrencies and when wallets are under maintance, which is for example actually on BTS, ARDR, BCN an Pink. Wallets must be updated on that coins and Poloniex seems not the fastest exchanger in updating wallets. Your DTR deposit should went through already, because wallets are working proper and you already had several confirmations. Sometimes deposits are showing only completed transactions and sometimes, when the first confirmations went through.

You could try BitPanda. Their fees are fair. You can check them here:
https://www.bitpanda.com/trades/buy
They also accept Visa/Mastercard, but not without full verification.
https://www.bitpanda.com/limits
For payment with Sepa and low amounts, you only need to verify email/phone number

Poloniex probably doesn't list coins on payment basis, like for example on yobit, Bittrex and Livecoin, but you can suggest new cryptocurrencies and if they meet their requirements, then they are listed.
https://m.poloniex.com/coinRequest

I used livecoin and never had deposit and withdraw problems, but never traded with Bitcoin Cash there, as preposter did.  Now I will also try HitBtc because they don't demand ID verification, when I understood that right. For security reasons I only give out sensitive data, when I pay out to fiat or trade on an exchanger of my trust.

That needn't be the same issue as OP's logging in problem. Many exchangers closed for new participants.
But never sent confirmation links for login in combination to changed withdraw fees and slow/no support aren't a good sign for a service like yobit and their customers.

Ardor is in Poloniex still under maintance, although it seems to be updated.
https://www.nxter.org/nxt-news-january-2018-i/#Ardor_Update
I would like to transfer them to HitBTC.
Does anyone know, what is going on?

Novaexchange had the largest number of altcoins. Unfortunately Novaexchange is closing. Now Cryptopia (or Yobit?) should be the number one with the most cryptocurrencies. But it will close Litecoin and Dogecoin markets, so several little cryptos will be delisted, I guess.
Edit: Novaexchange is contnuing, but deposits are still not available.

Additional to the warnings of chiggz, pumping is illegal, because you cheat other users. If you take part of manipulative pumping, you can lose your whole funds and be jugded. Is it worth it for a few bucks, if not your moralty hinders you on cheating? Learn to trade and you can make good profits in a legit way.

I don't like margin trading or forex trading. Day trading on crypto (excgange) has the big difference, that you will have all cryptocurrencies  in your pocket. The second big difference between crypto trading and forex trading is, that cryptocurrencies are still following an upward trend, if you choose established ones, because of growing popularity. So the probability is high, that, if you choosed a cryptocurrency and that went down, and you sit just the downtrend out, it will recover.

Good to read, that experienced members expect an upturn. I baught Ardor at 10000. For day trading. It was swinging between around 9000 and 12000 the last weeks and I wanted to sell them on 12000. Was only a bit worried, that there would ne something elementary, that caused the downturn. Now I will look deeper into Ardor and its project.
BTW: Why didn't Poloniex update the ardr wallets yet? Upgrade was finished already, as I remember right

Coinexchange seems to be up again, but I don't trust services, which sites are registrated anonymously, cheapname and P.O. Panama:
https://www.whois.com/whois/coinexchange.io
There are so many legit exchangers. Why do you use this one?

You are on a good way to get familiar with cryptocurrencies and being also part on ICO projects like electroneum.
Dogecoins are in my opinion good to hold.
To hold at least five coins is a good choice. Don't put all your funds into only one coin. It would also be good to hold a part of your funds in Bitcoin.
What do you mean with 5% profit?  5% a day, week or year?
I have devided my funds into two parts: Longterm hold of five cryptocurrencies and a very little part for day trading. If you also want to keep cryptocurrencies on longterm, don't keep them on exchangers but transfer them into wallets, where you own private keys.
Cryptopia is a good exchanger for beginners. You can learn about each coin at coin info section. In troll box you can gain some nice tips and in forum you can learn about the exchanger.
Also here on bitcointalkforum there are awesome threads about basic f.e  wallets, exchangers and much more.

https://bitcointalk.org/index.php?board=39.0