I haven't given myself any sort of budget. I used to spend a lot of money on tobacco and if I would have continued down that road, I'd be spending a lot more money on co-pays, home oxygen supplies, and maybe even chemo.
Money comes and goes in my life. Sometimes I have more than I need. Sometimes I wish I had a little more laying around so I could trade it for other stuff. When I'm flush, I spend. When I'm broke, I don't. - But no matter what, when I was a smoker, I always had money for tobacco and never had to buy generics or forgo the occasional expensive cigar. -- With vaping, it's sort of the same. I make sure i have plenty of juice, attys, cartos, and batteries around. Now and then, I'll buy myself a nice mod just like when I used to get a nice cigar.
I treat it a lot the same except for being supplied well. I never stocked up on tobacco. I didn't get in to a habit of buying cartons of smokes or boxes of more than a dozen cigars. I generally went and bought a pack every day or sometimes I'd grab 3 packs at a time if I knew I was going to be really busy for a few days, but I never stockpiled.
I am currently stockpiled. There's a thread about an ECFer who decided to do a 90 day spending moratorium and just consume supplies they already have on hand. - Even though I'm not keeping myself from buying things right now, I know for a fact I could survive many months on what I have stocked. It would be a bummer to run out of a few of my very favorite juices along the way, but most of the juice I have is quite vapable and would suffice.
So, I spend my money a little differently than I did on analogs, but just like cigarettes, I don't give myself a number of dollars and decide that's all I can spend in X amount of time on my habit.