Are there any differences in choosing a category for buying the sets?
Yes, of course there are. At the moment we have 6 categories for leveling up in Steam and one bot for exchanging gems

Very Low - To people who are just starting to raise their level: very low prices, the maximum level you can rise by using this category is 130

Low - To people who are just starting to raise their level: low prices, the maximum level you can rise by using this category is 170

Medium - To people who desire more, the maximum level you can rise by using this category is 250

High - Tremendous variety of sets, allowing you to achieve a high level. The maximum level you can rise by using this category is 500

Foil - For the metal set collectors

Summer/Winter - Exchange of sale collection cards. Activated during the summer/winter sale