What should be my upgrade priorities? GPU/CPU?

So I've saved up enough money to upgrade my system and I'm wondering what the priorities should be. I'll go into more detail about my budget below.

My current build is MOBO - Gigabyte B360M AORUS GAMING 3 mATX

CPU - i5-8400

GPU - GTX 1060 6GB windforce

RAM - 16GB 2666hz

SD - 1.256 Tb (2 drives)

HD - 1 Tb

I play a lot of games from e-sports shooters to AAA games and want the ability to play on high - max settings at 1080p and 60+fps. I currently have two monitors but mainly game on my 1080 144hz monitor. My budget would allow me to make a significant upgrade to 1 part or potentially smaller upgrades to multiple.

Cheers for any help you guys can give.