You can cook mince, then put it in a colander & tip boiling water over it, washes most of the fat off. Then you can cook it up with loads of veggies (grated if you prefer), add a jar of pasta sauce, it gives you a large amount of bolognaise with a very small amount of fat in it. Add to pasta with a sprinkle of Parmesan.

When I was having gallbladder problems, I bought a bulk tray of chicken breast, divided it into small portions, added some low fat marinades, and froze them in individual bags. Then I would cook them in a dry pan, and slice and serve in things like warm salads and tortilla wraps or enchiladas with lots of salad.

Fish is good, provided you don't choose oily fish like salmon (which is very good for you but might aggravate the gb). And spend a bit of extra time at the shops, I was able to find some relatively cheap low-fat versions of things, eg the local supermarket sold lowfat sausages that cost 50c more than the other ones.

I lost a lot of weight quickly eating like this and was quite hungry so adding in some no-fat yoghurt and low fat dairy like custard or rice pudding with a side of fruit helped fill the hole.