Good post, glad you are asking instead of staying blind!
Bittrex has been backed up for awhile and when another exchange (Binance I believe) opened registrations for an hour some 200,000+ people registered so you can understand the volume they are dealing with! Many people are also waiting for their preferred exchanges to open up.
I believe you can't go wrong with any of the big three BTC, ETH, and LTC. After that it gets crazy and I pay someone to give me some leads on specific alts. There is a crazy amount of false and uninformed information out there so cautious is good, don't get caught up in FOMO!
RE: My first investment into cryptocurrency.. what to do???