League of Legends (LoL) Question: Advice?

Just start playing it.

Assasins and Mages are generally played there so the biggest advise I would give is dont overstay in your lane with low hp, they pack a whomp so staying at 50 hp means they can burst you down and start taking over the lane completly.

If your unsure on the matchup take defensive runes and summs and maybe early MR/a zhonya's.. TP over ignite means you lack damage but can get away with losing a bit in lane.

Only take ignite if your sure about the matchup cause even though walking to the lane doesnt take as long.. If your up against for example an Zoe who can take close to your entire hp bar with one bubble and Q it sucks getting back to lane and having to base again right away.

If you take tp try and tp in on a minion thats walking behind the tower rather then to tp on the tower, alot of mid champs can still hit an ability under the tower and you'll get punished if they can. (I always try to punish bad tp's and nothing sucks more then getting into lane with 40% hp.

Alot of it is just getting experience, mute your team exept maybe the jungler if their toxic and just start your pratise runs. And dont expect miricles right away.

Taking plates can be dangerous since the enemy jungler has many angles on you under their own turret so take those only if you sure you can.

This is the first things that come to mind, hope it helps..
Its a super fun lane though, I love playing mages so your up for some fun! GLHF!