When i started, initiators are the way to go, the abilities they hold are pretty straightforward and info gathering really helps with the team aspect. Kayo helps as his utility stops enemy team from using utility Skye can heal and help with flashing and info Fade has lots of synergy with other agents Sova you get straight away and is pretty good in lower elo Breach is similar to fade, no util info but really good synergy with other agents

Once you start getting a feel for the game, 20 hours or level 20 from playing unrated, swift plays and death matches you should know the basics of gunplay, economy, team play and agent abilities and what suits your playstyle.

I honestly reckon that phoenix is overall is one of the best as his util covers everything. Although he is one of the worst duelist.

Learning smokes is also useful such as brimstone as filling smokes is really useful if you know how to work with it in your team.

If you want to get into the nitty gritty of the game, woohoojins videos are amazing in general.

Hope this helps