Hi, G2A will state whether or not they're steam compatible. You could buy straight steam gifts, However an unknown fact is that you can typically get significantly better pricing than G2A, Greenmangaming, Etc, by going through Russian/Ukrainian traders. The Russian/Ukrainian storefront are about 40 - 60% cheaper than the US/EU stores and this also applies to games on sale.
You can search for Russian traders, and Ukrainian traders through websites like:
steamtrades.com
Or you could shoot me a PM, and I'd be happy to arrange something. Cheers