Best Cheap Champions to Buy when saving up for expensive champions
I am a level 11, and want to buy a champion that I can enjoy and get good at if I don't like the week's free rotation. For example, I adored last weeks champion rotation (Akali quickly became a favourite), but this week, I don't really like anyone too much. While I have one gifted champion (Evelynn) I'm not a huge fan of her fighting style. Now, I'm saving up for expensive Champions (namely akali, and possibly Fizz, Xayah, and a few others) and would like to buy a cheap one in case I don't like the next week's champion rotation.
Notes on my playing style:
I'm usually a mid with assassin tendencies. I like to pounce on other players and deal lots of damage, rather than farming and thus I usually flit between lanes (though still usually a mid). Usually I like playing alone on my lane or almost alone, so not a huge fan of crowds. I have tried marksmen, and I did enjoy it too, but assassin is where my heart is at (Akali has got to be my favourite so far). Any advice on a champion I should get? I don't mind if it's a tier two price, as long as it's not in Akali's price range (3000+). I don't like overused champions, therefor please don't suggest Annie or Ashe. (I hated Ashe, and annie is way too overused). I really like champions with a low cool down or a dash like option preferably.

Top
Jungle
Bottom
Support
(top/bot/supp) you can get for free with an exclusive skin from Riot (If you don't own the champ you get it too. Garen you already get free from a starter Hextech Chest but you can still get the skin.) Just check out this post for info on how to redeem them;