Bgs have puzzled me for a long time, but my alliance mates helped me out in clearing a lot of things up and now I choose when I get payment but there are still a few mysteries.
First off doing bgs when your troops are not upgraded and you don't already have at least 2-3 mill power at your disposal don't even bother to grind them. There is a list of how much rss each BG lvl can bank, you should look that up. So basically what I do or did was bringing my mission bg to slight and a couple of bgs under my mission one until I wasted stuff I got from last payout and so I did it, it wasn't much... The mission always payed out but nothing fancy until one day by mistake I hit a non mission one It was lvl 80 or so and I got 2601 warlocks and 520 demons from it and was astound cos I never even invested close to that amount of rss, the mission one didn't pay anything after that for the first time, then I reinvested all of it and continued but it didn't work, the mission started to pay but it was ripping me off big time so just a few lvls ahead and I couldn't even bring my mission to slight.
Then I started tinkering with the many guides my alliance provides us with and noticed that the lvl 80 bg banks around 30 mill rss or so and when you count my warlocks and demons it was the exact number I remember. So after that I got my bank number or close to it, I stopped getting payouts from mission BGs and just slighted it then I would also bring down (slight) two or three bgs bellow my mission offense and my mission defense. Then I would just watch how many troops I loaded up for example I loaded up 40 mill of rss worth now I go and start finishing my slighted lvl 86, 87, 88 (cos thats around the max those bgs can rack up or pay out) and I get the payout from the first one I finish it's always occult two types and you get that when your bank is 90% full. Then I finish mission bg to bring me further up. I also stay on both sides cos it's easy to just run out of things to kill ie load up your bank. I load up stuff then when I run out of my payout I count it up and I hit for example lvl 90 defense non mission (cos I killed around 44 mill rss worth of my troops) and get my huge payout then I do the same thing and I hit lvl 91 defense also huge payout all in ocults two types then when I don't have any more defense bgs to slight I finish the lvl 92 offense one also huge payout now in more offense troops and now I kill all the offense bgs. I keep at least 4 bgs slighted at all times in case I don't get payed so I can hit mission one and get something to save myself. And this works for me.
There is just one thing that worries me a bit, each time I get that huge payout from a lvl higher I get more stuff than I invested, my latest payout was lvl 94 offense non mission 3601 necromancer (also by accident I didnt even load up my whole 40 mill rss when I got it), thats the exact 52 mill rss for that bg, problem is I didn't bank in that much to get that reward and it happens for some time now even before that I always get a little extra when I pick up my payout. I don't get if that's like a loan or something cos it was not my troops for sure and will it hurt me later on. I do keep track of everything that goes in and out, I have a minus (debt to bg) but I still get rewarded when I load up my last payout and hit the appropriate lvl of bg for my bank. I just would like to know how long will I be able to keep that up.