Most of the time it's depend on the total supply of coins , if it's under 100 Million under 1$ is really good price. means it has a potential of going over 1$, making over 10% from any coin/token is a good ROI.

Bittrex,KuCoin , HiBTC and sometimes if a token is(a bounty earned token for example) only traded in specific exchange I'll have to choose it regardless of benifits
Above ones are cool for me.
So far smooth and nice. No problems.
Not so far. security is great in all them.

How much? well there's no amount that can compare for it, different for everyone, a capital that you can take a risk with , or you can convert your earnings from other sources into BTC, that's what I do, every month a percentage of my total earnings convert into BTC and store in a secured wallet.

There are ICO watch lists from somewhat established crypto enthusiasts, some with lot of followers with them, you can find the recommended lists of them and choose coins that are common, it's the most successful way, than trying to find it ourselves. you can find them on twitter.

Some days are good, some days are bad that's the life of traders, and then there are really good days , and totally bad days, you just explained a situation like that. One thing you must practice as a trader is a spidy sense, a sense that tells you when to stop or when you hare having a chain of loses to take a break.

after 3-5 loses best thing to do is just STOP. stop what you're doing get up and go out, at least out of immediate environment, and do some fun things. and when you calm come back, do some Demo again, no matter how experienced traded you are keep wining on demo gives confidence for the moment and then start again.

It will recover, It always recovers, unless you're a day trader no need to panic from small ups and downs, smart day traders get the best out of it, most panic sellers go down with it. Collect and hold is what we should do now. In time that will turn into profit.

Not some, anyone knows about trading will say it's risky, It's all about practice , quick decisions, and sometimes LUCK, If you're trying to be a good day trader that means a lot and lots of training, playing demo, getting confidence. Until you fee you're ready.

Main reason it's risky is you can start loosing small but trying to recover most people tend to keep getting bad decisions and finally lost everything, best thing when you lose few trades is STOP, relax, and get off your chair and go out a bit, and before start again play more demo and get confidence again.

In any market  what affects the price is SUPPLY &DEMAND , considering the circulation is low and DEMAND is high for brtcoin that is the most affecting factor,  news from different government actions and rumours also can affect the price up and down time to time.