My wife has Sims4 and it's on an older HP i7 laptop with 8GB RAM but does have SSD for the drive (nice cheap upgrade) and the laptop has a better GPU than what you may have.
So in my view a SSD, be sure the RAM is in dual channel first. 8GB is enough.
So is the issue load time or graphic work? If load time the SSD will help in a big way.
Graphic work? See if you can fit the Nvidia 1050 in that machine.
Beyond that it's a CPU change and not what I suggest to most due to the possible issues.
Wanting to upgrade my PC, not sure on where to start first or what to get? so any help would be appreciated. I'm a massive gamer on Sims4 and facebook games and sometimes these can run a bit slow . I have posted a link to my computer details.