I need to remember to check this tomorrow and see if people commented, cool thread idea though.
I haven't really had major success myself because I haven't really done anything, but my minor success recently has just been being more productive than ever. I've always wanted to start a side business that could one day be a source of passive income so to that end I've been making my own t-shirt designs for a POD shop.
I've got about 20 designs right now and while they're all pretty basic in nature I think some of them have potential to do well. Right now I'm just trying to make as many of these designs as I can and then I can go back and refine them all later. I know it's a saturated field and I likely won't retire off it, but just starting something will feel good, even if I fail and don't sell a single shirt.
My niche I'm aiming for is Gaming, both videogames and D&D. I'm also trying to design some shirts that could promote the influencers I like to follow, I think tapping into an existing fan base would be a good idea to boost traffic starting out. So eventually I'd like to show them my ideas and try to get their go-ahead to sell shirts with their brand and cut them in on the profits. Need more decent products first though. For now this could be a failure or a success story! I'll learn from the experience though.
By all means anyone with experience with running a first business, graphic design, POD stores, Printful, Shopify, Facebook advertising, etc, feel free to give me any advice you have. I'll take all I can get!