Please Read this list of low-limit bonuses:
Your two main concerns when choosing a bonus are -
1.) Can I clear the bonus while playing in a within my bankroll?
There are Bankroll guidelines in a sticky under "Beginer's Circle", but the general rule is to have ~20 buyins for the game you play. At $300, you're BRolled for up to NL20.
2.) Can I maximize the bonus on my current Bankroll?
If your deposit only get's you $65 of a $100 bonus, sometimes it's worth considering leaving that bonus go until later when your bankroll is bigger.
That said, I think a good first pick for you would be Paradise because:
They have NL20 tables (not avail at Party)
You can maximize this smallish bonus on your $300 roll
You can clear the bonus (albeit pretty slowly)
The players are pretty easy...like Bodog.
The bonus never expires, so you can go at your own pace. You can even quit it for another site and then come back next year to finish the bonus.
Let us know how it goes.
Another reasonable good option for you is to consider doing some casino whoring (blackjack) to build up that bankroll so you can maximize Party bonuses and be BRolled for NL25.