Welcome
If you are planning on depositing only once- I would suggest holding off on that deposit and geting a little more comfortable with online play first. Play some freerolls and see how long you can last(although freerolls are filled with complete idiots, it still is a good way to get comfortable with online play)

Deposit once you are comfortable with the play and are able to count all the outs quickly and omfortably.

Definately get familiar with Bankroll Management. With 50$ deposit you are not rolled for anything higher then 2nl(0.01/0.02).
To play 20nl(.10/.20) you should have over $400 bankroll.
To play .25/.5 you have to have atleast $1k.
Now this is important, because even for a good player it is pretty easy to lose al his money by not following the Bank Roll management rules.
Take it slow and beat one level at a time and you will be playing the .1/.2 in no time.