It is definitely an upgrade gaming-wise however, it would be a lot smarter to save up some money and get something better. A 750 Ti barely holds up at 1080p anymore and will probably get outdated pretty soon leaving you wanting to upgrade again. Like don't expect to be even close to maxing out any recent games at all.
If you can get an RX 480 for a decent price, I'd save up for that. Doesn't really make sense to get anything else right now if you can get GTX 970 level performance for 200 USD. Check the pricing in your area and if it's good, I would save up.