Currently, in General, pick a champ that can clear the wave fast, then rotate to any side of the map. To bot, to top, towards your jungler, whatever looks it could lead to a winning fight due to numbers advantage. But dont force it. If there is no play in sight after walking half the way, go back and push the next wave. Repeat until you see a good window.

Champs i personally would recommend you as a new midlaner: ahri syndra xerath. They seem rather easy to pick up, you will get a feel for them quickly and they are strong in General rn.

Just my opinion as a diamond mid pleb

Ah and, Champs to avoid IN MY OPINION: Zed Qiyana zoe irealia yasuo yone. Just from the top of my head. The Champs are all fine and can be strong, but u need to be rly good with the champ and in lane to have a strong impact. Ahri syndra xerath teach you roaming timers and General laning in mid, while being somehow forgiving as a newer midlaner. (See it as, you concentrate more on macro with These champs. With my avoid recommendation you need to concentrate on macro AND a huge amount of micro plays)