Welcome to the forum.
Sorry about your diagnosis, UC sucks that's for sure.
Lots of folks here have had some success with the SCD diet, specific carbohydrate diet - which is pretty strict.
So, I would recommend you start off by being dairy, wheat and gluten free to start off with and then see if it helps you. I agree subdued about the food journal - it will be the only way to really definitively determine what really does not agree with you.
As far as supplements are concerned:
a good probiotic like VSL#3 is important, L-GLutamine in large quantities for colonic repair, slippery elm bark powder for healing.
Have you had your Vitamin D and B12 levels checked?
Are you on any rectal meds?
Dx - UC 09/2010.Tried various Mesalamine enemas/suppos/pills with Prednisone for several rounds without any help.SCD Diet of proteins,veggies,salads, fruits, & protein shakes w/almond milk, Liquid Minerals& Vitamins,Maca powder,L-Glutamine 15g, D-Ribose 5g,L-ArgEthylEster,chia seeds,VSL#3,K2,VIt. D3 100,000 IU every 10 days.Canasa suppos. as maintenance.Transdermal LDN is working! I feel great!