Here's the way I do it. Definitely not the most nausea-free method by a long shot, but I find it to be effective and reliable nonetheless. I take 4g syrian rue and crush it up (with a spice mill) and stuff the crushed up rue into gel caps (the bigger the better, try to get "00" so you don't have to swallow as many). Then I'll poke a few holes in the gel caps. Sewing pins or thumb tacs come in handy for this. Then you can dissolve DMT (I would start with around 50mg, but you may find it weak, and thus work your way up slowly in the future) in orange juice. I like to take the gel caps of syrian rue first, wait 15 min and then drink the DMT-OJ. Normally I tell people to smoke a little more DMT (only like 10mg) especially if they're not feeling much and it really kicks things to the next level, but if you really don't wanna smoke, and you notice effects but they're not as strong as you like, I suppose you could try taking some more DMT in OJ, but I'd really recommend just 1-2 hits of 10mg if you're up to it. It's really something else, and my favorite parts of life have happened after vaping 10mg on a pharma session - pure bliss and beauty.
I personally don't mind the purge (too much), but if you're going for nausea-free, then you'd wanna extract the harmalas from the syrian rue or caapi and convert the freebase DMT to DMT-fumarate using either FASI or FASA which I believe are in the wiki as well. Freebase DMT will make you nauseous as will syrian rue or caapi. For me purging is part of the experience.