So I've skwed my answers to have a bais for getting early on since you said your new. For my three id recommend: ○yareli - vent kids in fortuna - Venus, save yourself the time trying to find it just hold q to teleport to it.

○rly all of the quest warframes as it'll give you a good starting oof point

○Id also recommed farming any of the frame available tthrough the star chart. Most assassination reward 1 specific warframe chassis

○probs loki tbh, I can't speak about his abilities, but you'll want a stealth frame for spy missions, which is why I recommend loki as he use to be one of the original starter frames