Ya ba dibba dibba dibba dibba dibba dibba dum!
Oh wait... this isn't Fiddler on the Roof.

Any time I've had disposable income, I've never been any good at spending it on myself. Sure, if I was at a level of affluence where i was RICH, I might upgrade certain things in my life. Get a nice bed, replace broken or breaking things, make sure my partner was comfortable, overhaul my audio set up, maybe invest in singing lessons, update my wardrobe. But I was never one for making grand purchases.
Maybe set up a VTuber agency for VTubers outside the norm like fat VTubers like me?
PAY FOR A DAMN EDITOR AND A MANAGER. I badly need both of those but I can't afford either ;-;

My money tends to go towards supporting people. I love making sure people have the freedom to express themselves and create their art without having to worry about not making rent. Our community is held up by its artists, writers, game developers etc. I don't have much in the way of money now but most of what i do have goes back into the community through various Patreons etc. So I would probably just do that on a larger scale. I know what its like to struggle and I don't want anyone to suffer that.
Top tier on every ones Patreons. Anonymously dropping batches of gift subs and bits to VTubers who've been working hard. Paying artists and writers to draw or write something they've always wanted to do but haven't had the time because of other commissions.

Maybe buy a mansion to turn into my own personal harem of feeders and mutual gainers where I can be Queen Feedee and make sure all feedees can have their needs seen to who couldn't afford to previously...