Quote Originally Posted by IAmFilipe View Post
Besides I'm playing 25NL and don't really need to worry about advanced concepts like mastering Implied Odds and All-In +EV at this level right away. Or am I wrong?
Wrong -- these aren't advanced concepts, they are fundamentals. You need to understand them even if you are playing 2NL. The good news is that they aren't that difficult to learn You can find threads dedicated to them in the Beginner's Digest.

And is really necessary to have 100 buy ins at 2NL and 5NL, I just honestly dont feel like I'll lose 100 buy ins in a row at these levels, although I'm sure plenty of new guys say the same thing
No, at the lower stakes you can move up once you have 20 or 25 buy-ins. But set a realistic drop-down amount -- like, if you move up to 10NL with 25 buyins but then drop below 20 buyins, go back to 5NL until you have 25 buyins again. Also, the higher the limit, the more buyins you should have simply because your edge gets thinner and thinner (less fish), so you may experience larger swings.