I don't have a budget per se, but each pay I just scrape my leftovers (after mortgage, bills etc etc etc.) into my savings account and that pays for toys as I want them.
As others have mentioned, there can be long gaps between purchases because new toys aren't released every week - they come in waves. So when a new wave comes out I'll spend up, but then there will be a time when the spending goes down until the next wave is released. e.g. Wave 8 of Studio Series just hit stores, which is why you'll notice that I've made review threads for some of these figures (Bumblebee, Soundwave) -- I'm picking up Arcee later this week too. But yeah, after that it's pretty much just wait until the next wave hits.

And yeah, occasionally I'll buy something here or there, or I might pre-order some stand-alone toys like MP Spinout, but generally that's how it works. Save money during the ebbs and spend during the flows. On the whole I tend to save more than I spend because most of the year is spent waiting for new releases. And I have to admit, I've been saving a LOT during this whole COVID19 isolation thing - not surprisingly because I'm not going out or socialising etc. anymore, so suddenly all the money that I would normally spend on petrol, eating out, movies, travel etc. is just being saved instead (so I've made a handful of impulse buys like getting a loose MP Forty-Four (pretty cheap though)).