Many people have issues with digestion. Here is just a skimming touch of a few suggestions that I have found helpful.
Go for Good Bacteria
Number one on my list would be eating raw probiotic ferments and cultures, such as sauerkraut, kefirs, kombucha, yogurts, etc. These will provide good bacteria for your gut, which greatly assists digestion, as well as neutralizes bad bacteria and boosts immunity.
Try Soured Grains
Here is a great link for soured grains. She has the starter recipe for porridge, as well as how to feed it.
I just add a tsp. or so of either kefir or yogurt culture starter powder to 3 cups of water and 2 cups of grain (steel cut oats), to make the starter mix. This gets the ferment going, since I do not have whey like she suggests. Leave it covered on the counter to ferment for a few days, until it gets a bit bubbly. Then you can put it in the fridge in a glass jar.
To use it, add a cup or so to your porridge mix (grain and water) in the evening and let it ferment on your counter overnight. Cook it in the a.m. You will want to also replenish and feed the culture starter to keep it going.
Yogurt or kefir starters can be purchased in the cooler section of a health food store, or natural food section in the regular grocery. Of course, everything soured, like sourdough bread, soured milks such as yogurt, kefir and cottage cheese (if you tolerate milk), are easier to digest.
Avoid Improper Food Combining
Improper food combining is a big challenge for most of our ways of eating!
Basically, the rule is: never eat animal proteins with complex starches. You can sometimes get away with cheese, butter, eggs or milk products, as opposed to any kind of meat.
The stomach needs a real acidic environment to digest meats and an alkaline environment to digest starches. Because these cannot be present at the same time in our stomach, it wreaks havoc with digestion if you eat starches with meat.
So lots of greens, salads and most non-sugary or non-starchy vegetables digest well with either starches or meats, but never with starches and meats together.
Learning how to make vegetarian dishes is often helpful, when you have things that mix meats and starches (lasagna, pasta, rice casseroles, etc.). Remember that quinoa, chia, and hemp seeds, are all complete proteins.
Fruits only go well with greens or non-starchy vegetables. Here is a great chart that will give more details.
Pre-Soak Your Beans, Nuts and Legumes
Always pre-soak your legumes, beans, nuts etc., and throw out the soaking water since it has enzyme inhibitors and phytic acid in it. I soak almonds, beans and legumes 12 to 24 hours and other nuts and grains just 1 to 4 hours according to hardness. Flax and chia seeds would be the exception to soaking, since they create a gel, which is beneficial. Here is a link with more complex information on this topic.