Switching roles
So I've typically always been a top lane tanky / supporty type player (scrub teir bronzie) but lately ive decided to begin to improve my ranked play because i know that im capable ive risen from b5 after placements to series b2 in about 50 games. However I am seeing that I need to take on more agressive Champs to continue to develop as a player and I would like to hear from peoples suggestions
currently playing

Zyra naturally counters almost every other Support in the lane. Her poke is ridiculous once you get used to using her abilities.
Nautilus works well in both Top and Support, as well as the Jungle if you know how to do it. He has a great gap closing grab and is one of the strongest initiators on the Rift.
Perhaps the most popular raw initiator, Thresh's kit allows him to pull off a vast array of plays that no other champion could even hope to. However, his skill cap is among the highest in League.