I've been at this game for over 10 years now and I can tell you what you guys probably already know, its hard as hell to make a profit against the books. Lines have become increasingly efficient and any edges are sniffed out and quickly eliminated, even in smaller markets which I have specialized in for years. This has forced me to look elsewhere to look for positive EV opportunities.
I suggest trading stocks, not just any stocks, but stocks that are primarily traded by humans where edges are easier to find. I've back-tested several strategies against small cap (under 500 mil) NASDAQs and have found great edges (10% or more) consistently and my tracking of trades over the past 5 months have produced similar results.
I still love the action of a sports game but the high quality opportunities have dried up over the years and I expect it to get worse.
If any of you guys are fed up with sports and books in general, learn another craft where you actually have a chance