Could someone with some ranked experience (1500+ elo for example) please suggest to be viable and difficult to counter mid champions? For example, I know Elise, Katarina, and Anivia are very powerful midlane. What are some others? I want to get to 1600 elo or higher but seem to not play very "viable" picks such as Brand. Please and thank you!

I would say Fizz. Many people don't know how to deal with this guy. He can also, if timed properly, dodge the majority of an AP Mage's burst.

Unfortunately I'm limited on IP.

Here are the champions that I own that can go mid lane.

Annie, Kayle, Katarina, Morgana, Karthus, Kassadin, Cassiopia, and Teemo. Which of these are good for the midlane and are better?

Maokai. Get enough AP so that one sapling destroys an entire wave at level 5. Now proceed to get 100% CS without every getting ganked.

Buy a Warmog's and you are GOOD TO GO!

Another champion that utilizes the same concept is Sivir. You'll need to buy a Wit's End + Malady though, because if you don't deal magical damage in the midlane, the meta police will come and lock up your Elo.

Hahaha Mynt you're funny.

I kinda think I should master Annie, Kayle, and Katarina if I wanna do well in mid.

Kennen, is super strong, brings alot of damage, utility and can go anywhere, and can go even on any matchup

edit 1: of the characters you posted kayle, morg, katarina, and karthus can go against almost anyone, morg and kat are especially good in solo queue

Thank you so much Saeder!

Ahri is a very safe pick, her ult has so much mobility.

Kennens e makes him very hard to gank and he can get pretty consistant stuns.

Kass is also hard to gank with a ~5 second flash ult.

I really love Morgana and Kayle. I find them very fun and easy enough to do well with.