What you should do first is to download and install msi afterburner (don't worry, no overclocking or anything, we only need the graphs for usage!).
Then do some racing like you normally do and then go into afterburner and tell us your gpu load. It shows the last 5-10 minutes at default settings I think.
We need to find out if a new processor will gain you anything or if the gpu is above 90% while you're driving, a new graphics card would be better.
My estimation would be that at low settings, the 1050ti will be good enough though.
But settings don't make much of a difference for the processor so a better cpu should be a good upgrade.
As for the cpu:
There's only one choice: 4c/8t k-model.
To actually see a difference you need the 8 virtual threads and definitely the higher frequency of the k model.
So i7 6700k it is.
BUT only if you get it really cheap! (probably used).
Also: what motherboard do you have? Only important for overclocking but these processors gain quite a lot from it so if you don't have a z chipset and can't get the cpu for less than 150€, getting a completely new set of mobo + ram + cpu will be a way better deal!
RAM: you say you have 8gb. 1 stick or 2 sticks?
2 sticks will give you dual channel, which definitely makes a difference! 32gb are useless for most people so if you have 1 stick, getting another 8gb stick (best would be same model or at least same voltage and timings) and just put that next to the other!
Overall I fear that buying the ram and the i7 6700k will be too expensive to be a good deal..
Selling your mobo +ram + cpu (+cooler) as a set and buying a i5 9600k + z390 mobo + 2x8gb ddr4 3200 cl16 would be a looooot better!
It's the best bang for the buck for simracing right now! Almost identical single core performance as the latest 10900k and since all simracing titles don't use more than 5 cores, you get full performance for kinda low budget!
Hope that helps