First of all, welcome to the crypto world!

Now lets talk business, as for Bittrex, I recommend that you go do yourself a favour and register in Binance (as of the time that I am typing this the registration are open). Binace si like Bittrex but simply better and bigger with more coins available!

As for investment, you have to choose what are you looking for. Do you want a 100%-200% back on your investment (x2 to x4) ? If yes, then go for Ethereum ETH no hesitation, its a safe bet. If you want to take more risk, go for altcoins that are currently in the top 50-120, they have a lot of place to grow. I would recomment 0x (ZRX) it's in between the high risk and low risk and has great potential!

Of course, always do your due diligence, and do your research on a coin before investing and never invest more and what you are willing to lose.

As always, invest wisely!