So I've used, and burned through, a whole bunch of different rotary tools over the years. I've got a couple life lessons out of that which I hope are useful to you.
The worst possible value, in my opinion, are the Dremel branded rotary tools that are below their "professional" line. The professional ones last quite a while for me, but ultimately it is the speed controllers on them which go. You can usually get rebuilt ones on Ebay for significant discount.
https://www.dremel.com/en_US/products/-/show-product/tools/4000-high-performance-variable-speed-rotary-tool If you want to go cheap, these actually have better build quality than the inexpensive Dremels and are pretty good. Lower top speed, less overall performance, but they are awfully cheap. This has given rise to the frequent phrase in the shop "give her a TungFull" when something isn't working and requires a rotary tool to fix. If you do buy one of these, be sure to specify the American plug type:
https://www.aliexpress.com/item/33002837217.html Here is the thing though, electrical rotary tools have high gyroidal force and are heavy, which makes them hard to handle. They also spin relatively slowly, and overheat relatively quickly. All that they do well is produce relatively good "low" RPM torque. If what you're looking to do is super fine work without the tool catching and driving, without huge hand fatigue, etc the tool you actually want is a pencil die grinder:
https://www.amazon.com/Astro-218-8-Inch-Pencil-Grinder/dp/B000RH36WU/ These things are MUCH faster, more reliable, easier to handle, and don't catch or jump. In short, they do what a rotary tool does, they just do it better. The real key is that rotary tools are too slow and so the bits have a tendency to catch and jump. These pencil die grinders are fast enough that doesn't happen. Be wary though, at max chooch they can also spin some rotary tool bits to destruction. There are some things they don't do, namely the whole low-RPM torque thing, and they are quite air hungry, so I do keep a fleet of rotary tools (and larger die ginders) on hand as well. That said for 90% of jobs the pencil die grinder is the tool I want. It is just that much more precise.
As far as bits go, you'll just have to experiment and see what you like and what does what you need it to do. Generally all the bits are short lived, so my best advice is to get a MASSIVE kit and just see what you like. Whatever you start burning through, just go back and buy a bunch of that specific item. If you don't have a big kit, the problem is you'll always need precisely the part you don't have. So something like this:
https://www.aliexpress.com/item/32688183307.html There are two types of tool though which are used so much you ought just buy a bunch straight off. The first are the abrasive cutoff wheels. Something like this:
https://www.aliexpress.com/item/32839322694.html And the second are the carbide burrs. Also invaluable. If you use a rotary tool proper (electric) you'll probably want these:
https://www.aliexpress.com/item/33003379821.html However the die grinder tends to prefer these for most cases:
https://www.aliexpress.com/item/32805004892.html I hope that helps. Again just my meandering experience having countless hours on these tools now. Take it as worth what you paid for it, which is to say even less than a cheap Chinese rotary tool.

Also I don't mean to endorse any particular store or vendor for any of these purchases, buy from who you like where you feel comfortable. These are just single examples in a massive industry full of stuff all of which was made in China.