Pretty New Here, L4 a Group / friendly community / & Information

you can buy keys from humble bundle or fanatical or any other official authorized key reseller

just make sure the game doesn't have ** next to it (indicating it is/was a free game) when making a giveaway or you get no contributor value increase so it won't increase your level

For groups and whitelists, read
https://www.steamgifts.com/discussions/group-recruitment
https://www.steamgifts.com/discussions/whitelist-recruitment

Take a look if the group or whitelist recruitment is still active (thread not saying "closed", last comment within at max 3 weeks or so, creator of the thread not offline for months or years). If the thread is still active, check if you meet the given requirements. If you do meet them, follow the instructions how to join, most of the time this means that you have to write a comment in the thread.