I have winter bib shorts from Decathlon and they are pretty good. Maybe not as good as the premium brands, but I’ve had them for 4 years now and they’re fine.
To be honest, some cycling kit is very individual. I think it’s fine to buy budget kit at first especially as you’re still working out what kit you want/need. For example, if you buy cheaper winter bibs, and use them a lot, but they don’t fit well etc, you can still save up for expensive ones. If you find you rarely use them, you haven’t wasted too much money.