Welcome back! You'll find a lot of us here are ex-slotters who re-discovered the hobby years later. If you are interested in both 1/32 and 1/24 then I think Carrera is your bet...I'm guessing you already know that from your post. Carrera, speaking as a guy who has owned a whole lot of it over time, is very high quality and worth every cent you have to pay up front. It's true there are less expensive, and also more popular, brands. But I think you can't go wrong with Carrera...and most especially if using multiple scales is a priority.
Having said that, I'd recommend buying one or two boxed sets to start with...that will get you all basic equipment at a reasonable entry price. The sets will be filled with R1 turns...try to find sets with as many R2 or even R3 as possible. They will come in handy later. Also, you'll probably want Borders for your turns (especially when running 1/24 scale)...so it's a plus if your boxed set has some of them as well.
A couple things ongoing...watching Ebay for used Carrera at cheap prices (track, borders etc), maybe getting Track Planner software (several are free including Carrera's), also you may want to read up on covering your shiny stainless steel "power rails" with copper tape. If you have a track layout you will be keeping for a while, copper tape can do wonders for conductivity and also reducing noise.
Ok, well...I'm sure you'll be getting a lot more advice. You've found a good source of it here. Have fun!