If you're just new, get to grips with the site you wanna use by playing the play money for like 15 minutes then go to the 2 euro/dollar cash game and practice there! Poker is an interesting study because you get to choose the price of your education!
If you want to concentrate on tournaments or sitngos or cash then you need to play the one you like! Whatever feels fun to you is where you should start! In cash you can leave whenever you want whereas in tournaments you have to make sure you have a couple of hours free!
As for study, search gripsed on YouTube it's a good free resource!
Study a little, play a lot, keep the stakes low and have fun!