@Megla -
Keep in mind that I have only been doing this for 10 days....
I read an article about MLB dfs and it said that wOBA is a great stat to look at for cash. I found a site that factors in the park in that stat, and a separate one where they factor in the pitcher's wOBA allowed vs handedness of battter. So I have been looking at those and writing down the top 4-5 at each position. Then I do look at power and anybody that has decent power vs. handedness of the pitcher moves up. For tie breakers I factor in if they are away (to guarantee the 9th inning bat), batting order, and projected run totals for the team. Then I see who I can jam in with the salaries. When I did this today, Mets, Balt, and Oakland batters were all over the lists.
Gpp I have been looking more for the power upside and do a similar list for that and see if there are 3+ guys from a team that show up. If I scratch my head as to why, that is usually what I look for in gpps. Also I have been looking at Pitcher splits and stuff like HR/9 innings, WHIP for handedness of batters, HR/FB rate, etc... to see if there is a team that shows up on multiples of these, again, especially if I think it looks odd. As people have said, Milwaukee and Cincy show up here, but that is probably popular. One that showed up that made me think gpp was TB with a lean to the righties and same with Oak RHBs. Also KC LHBs.
I get what you are saying about Bumg for gpp. I have been surprised how much lower the stud is owned in gpp b/c I assume people go cheaper to fit the huge bats in. I will use that stud to pair with a cheap stack - ie Oak players that average about 3k each.
Everytime I have tried the "can't miss" games of the night for stacks I have whiffed - ie Col/Milwaukee last week, Coors field, Toronto last night. I have had more success with a cheap Philly, Balt, or Met stack so far. As you said, that might even out as the bats warm up on the season.