Two ways of looking at it: if you have unique content that you think is valuable and people would want to keep coming back to, think of a memorable brand name. If you are going with content that is more aimed at passthrough traffic and perhaps similar to a lot of other sites then go for a name with keywords. No more than 1 hyphen in the name. The latter is easier to get ranked in the shorter term, but the brand name is far better for loyalty over the longer term.
Pick an extension that suits your taregt market. If you are aiming at “the world”, get a .com or if that’s hard, a “.net”. If primarily UK, then a .co.uk etc etc. Try to avoid generics like “.info” or “.biz” as they are harder to rank and make sure the domain is hosted in the country for your main target audience.
Oh and by the way, as a player crossing over into affiliatedom you have a head start – welcome 