Best sites for online money backgammon: GamesGrid (#1 by far), followed by TrueMoneyGames (run by the Snowie developers), GammonEmpire, and WSEX (run by some English bookmakers). If you play for more than $10 a point, you will almost certainly be playing top players who have trained themselves using Snowie and Jellyfish, the two top backgammon programs.
If you're serious about playing for money, you need to get Snowie, both as a learning tool and as a way of analyzing your matches to see if you were unlucky or if you were outplayed. Most sites allow you to save a copy of your session in Snowie format, which you can then download and input into Snowie for analysis. It then gives you the average error rate (in millipoints of equity per move) for both you and your opponent. (You can get the same information for yourself by playing against Snowie for practice and analyzing the session.)
Here are a few guideposts on the error rates:
12 or higher -- beginner
8-12 -- average player at $1/$2 per point
5-7 -- average player at $5 per point; average player in the top section of major tournament.
3-4 -- average player at $10+ per point; top 20-30% of players in major tournaments.
2-3 -- typical opponent at $20-$50 per point; top 10% of all major tournament players.
Hope this helps. You can get Snowie at
www.thegammonpress.com online.
Keep in mind that at backgammon, skill dominates much more quickly than at poker. If you're a beginner and you play 20-30 games sessions against a top player, you will come out ahead in very few of them.