Security is a major thing you need to be aware of. Think of crypto as cash. As in you probably dont want to keep your life savings in your back pocket - way too easy for someone to walk off with it. You also want to be careful who you trust with your coins because there are very few laws in place yet to protect you. Security is YOUR responsibility. If you have a large number of coins you probably want to move them to multiple paper wallets, make copies of said wallets and keep them in separate, safe places like a bank security box. SMaller amounts you plan to spend in the near future you can keep on a computer/mobile device but you want to be careful.
As far as what coin, thats up to you. Bitcoin is the biggest and most wide spread. Litecoin is second and this is a litecoin forum so a lot of people will point there. Personally I have about 65% in Litecoin, 30% in Bitcoin, and the rest in a few other coins that I just ended up with over the years. I didnt pick those numbers, its just how things have played out. I have been slowly increasing my Bitcoin holdings this year but I also have spent more Bitcoin this year than in the past (actually bought things, not cashed them in)