stop using bottleneck... some games stress CPU more, some does on GPU. Both cards are fine with your cpu, what is your current card? PSU?
You can get gpu for now since it will boost performance immediately and you can reuse it to upgrade CPU in the future.
my current card is an gtx 950 2GB (i think ist a lp version but im not sure, because i bought it used for 300$)
and my psu is 420W
Is a 1050 ti enough for 1080p gaming? would be nice to play the most games(like rainbow six siege) at max settings.