My question is how to gain weight if you're a raw vegan for other health reasons?
i.e. - Starch, sugar, meat, dairy cause me inflammatory problems (very painful and debilitating), sinus problems and mental clarity problems.
Lots of avocados and nuts?
oh dude, yeah, same issues, mostly. For me I have celiacs, so it's not starch for me, just gluten which sucks because I can't advantage of a lot of the staples of grain awesomeness - I simply cannot physically compete with a runner on a whole wheat diet for example. But yeah, it might just be a gluten thing: try allowing yourself gluten-free starches and see how that goes.
For a while last year I was working overtime on a manual labor job and I was cooking all the time. It was ridiculous trying to fill 4000 calories a day on a roughly vegan diet, here were the things in that diet which were in starch but could still be used as bulk-up fodder:
Oat bran. Go for 100% Bran muffins. If you don't like the oat bran go for the wheat bran or rice bran if you're good with gluten. Two big muffins every day for breakfast. When you're baking it, load it up with ground flaxseeds and nuts, and make sure to give it plenty of that canola oil, don't be stingy now..
Quinoa, Hominy grits, dal, gram and sorghum all worked a charm. I'm no longer working that job but I still make gram rolls every week. 10 minutes throw in the oven.
Tofu, sesame-based stuff, expensive; but you can load up on raw soybeans, beans, and lentils for cheap if you're ready to cook. I can have lots of cooked legumes in one sitting, but I don't like having them more than once a day. So if you're trying to bulk up just have a huge rice and beans dish for dinner. Shovel it in there fast before your stomach starts getting sick of it. :D
And of course, to repeat everyone else here: Peanut butter: phenomenal, barato, put it on everything for flavor. Get it no-salt so no worries about having it by the bucketload.