Firstly, your topic title is bad. It makes me guessing that you are asking for help. In fact, you are teaching others about your methodology to invest.
What is Cryptocurrency?
Cryptocurrency is a digital currency that is decentralized and encrypted to enhance privacy. Bitcoin, the first of its kind, is based on blockchain technology, a decentralized and transparent ledger system.
Not all cryptocurrencies are decentralized and not all of them can protect your privacy.
Where can I buy Crypto?
You need a place to buy your desired coins and a place to store it. The most popular place to purchase cryptocurrency are cryptocurrency exchanges, there are several exchanges to choose from, such as binance, coinbase, kraken, paxful e.t.c.
Choose biggest exchanges and most trusted ones to trade. Don't store your crypto on exchanges longer than what you need. When you finish your trades, withdraw your crypto instantly to your non-custodial wallets.
To store your currency, you need a cryptocurrency wallet, which is necessary to securely store the code that makes up your coins. You can use electrum wallet, blockchain, or you can use a hard wallet.
Hardware wallet, not hard wallet.
Also you forgot about the importance of non-custodial wallets.
How Do I know which coins to Buy?
The most popular crypto right now is Bitcoin and Etheruem. They are always a good buy.
It depends on the market phase: bullish or bearish and how long you are planning to let your position opens in the market.
If you are looking into alts, you have to do thorough research before buying any cryptocurrency. There are lot of scams out there. You should check the coin cap, read the white paper and see if you're interested in the project. Don't just listen to rumours and tweets. Things are usually in fast motion in the crypto space. I honestly cant give financial advice on this subject but I'd suggest if you're investing in a coin you should look at the tech behind it first and then the publicity.
Scam developers are good to polish their documents, white papers and outlines very promising roadmaps. Investors are not IT guys so they can not understand technology behind cryptocurrencies.