not really, thats like saying "Painting this house before it is finished being built should be the first priority"
Its a waste of time and resources to put so much focus on optimization when half the code could change in the future. better to have your game feature complete and then make it run like a dream then waste 3 months making it run like a dream only to have to re-do all of it when you add a new system.
also using a $99 budget CPU from 6 years ago and expecting high fps on an early access game is absurd.
As for the OP, what moppel said is probably a really good option.
I would upgrade your GPU last, once you have a new mobo and cpu you should notice a decent increase, then you can sell your 760 and put it towards a new one later.