I'll agree with most of the above. I stick to 1%-2% of bankroll, play within that range for all plays (so you can say I only have 1, 1.5 and 2 unit plays)
When sizing your bets, use your total bankroll, not just what you have in one particular book.
Take advantage of low juice and bonuses.
I think 3 books is too few. I would use at least 5:
at least one sharper book (pinny, 5 dimes, olympic)
1 square book (SIA is best, bodog is also OK)
Then look for a few books with opinionated lines...I recommend Carib
Between these first 3 outs, you should be able to get the best available line at any time. Add in 2 more books that might have something else you are interested in (low juice, bonuses, free half points, etc)
Remember with your %1500 bankroll, you will only be betting $15-30 per game. Don't give into the temptation of making bigger bets because your bankroll is growing too slowly. If you start playing $75-$100 per play on this bankroll you have a good chance of losing it all.
Monitor your bankroll on a weekly and monthly basis and see how you are doing. You need to have the patience to grow it slow.