Been playing it off and on since last NFL season. Definitely not a good thing for casual play - it takes quite a bit of research to make any sort of a decent payout, especially if you are wanting to play in the "big money" tournaments. Baseball is the worst in terms of the amount of research it can involve Sure, you can get lucky, but it won't last - research is necessary...
All the big tournies have the usual sharks who enter 100+ lineups in each one, and those guys are usually, but not always, the ones who rake in the big dollars. One of the recent million dollar PGA ones was won by someone with a single entry, so it can happen.
I've been playing with MLB daily, usually throwing in cash on the Quarter Arcade tournaments, quarter leagues, and the ticket qualifiers (top finishers get a free $3, $5, etc. ticket for any future event or a bigger ticket for a specific tournament) and playing my tickets in bigger ones. Its fun, but you won't get rich on the little ones like that. Just stockpiling tickets and such for NFL season mostly, with the occasional $100 week here and there.
I won two $20 tickets for this week's PGA millionaire maker, so maybe I'll be the next one. (I will win about $2 - can almost bet on it)
There is also a Reddit group for DFS that has several links to resources like weather, odds, etc. The group is /r/dfsports.
/r/sportsbook can also have some good info from time to time.
Jonathan Bales has some pretty good books on the subject, and at least one is currently free on Amazon.
http://smile.amazon.com/Fantasy-Foo...pebp=1436891163794&perid=1CQSBTMFHJNZEC61X5SY