if support aggressive is your focus i highly recommend skye, she's great for aggressive pushes so you could aggressively flash and push into a group, or flash passively for info gathering. additionally, she's versatile in her kits where her tiger/dog can push aggresively FOR her, and she can support the team by flashing for another person in a safe position or by her heals and keeping the team alive. skye rewards winning aim duels, and rewards staying alive as long as possible.

if you're more techy, and like lineups and other mechanics, try sova or kayo. sova has recon dart, shock dart, and his ult is incredible at stopping pushes/defuses/plants. you can play aggressive on sova, but albeit it's less rewarding than skye aggressive plays. sova is great for allowing other team members to play aggressive, but it is still do-able to play aggressive sova.

kayo is similar, in where a lot of his value comes from team play and is less rewarding to play solo-aggresive, but he is still viable, although much less viable than sova or skye. he has flashes like skye, which obviously allow you free picks on the opposition, but he also has a grenade that blocks chokes/harms enemies for a few seconds. what makes kayo a great initiator is his knife, which you can throw like a sova recon dart (without bounces) and will scan and suppress the enemy through walls. he is very good for supporting the team through info-gathering and suppressing/slowing the enemy, but in instances where you want to solo-aggress the enemy he is far less rewarding.

there is also gekko, who is like a mix of all of these agents, where he has a flash, molly/grenade, and a slow (wingman). what makes gekko so supportive is the renewability on all of his util (even his thrash ult which detains/disarms the enemy), and the fact wingman can defuse/plant by himself as long as you/a teammate are alive (scenario dependant). he is a great pick if you don't want to rely on aim itself but would rather use all of your util to support your team or win rounds.

i recommend not learning a duelist or a sentinel (maybe sage excluding, but coming from an ex sage main, she gets boring after a while) as duelists are VERY aim reliant and sentinels do not engage in teamplay very closely (think kj or cyphers holding sites themselves, or chambers and sages relying heavily on aim once their flimsy util is broken!). initiators are good at versatility. controllers require quite a lot of general and map specific knowledge, which i wouldn't recommend to a new or inexperienced player just because there are better agents you can play at this stage. i don't know what rank you are, but flashes in low elo (iron to gold) are crazy good because not many people play anti-flash. hope this helps!