He is a very solid player; on my St. Etienne save he improved regularly with game time, but he didn't reach the potential of an Nkoulou or M'Vila. I would say that he would be a good player for Europa League sides in a couple of years.
First season?
Maybe Paulo Henrique, or potentially Josue on the cheap to bolster the centre of midfield.
Or go with youth, M'Vila develops well, as does Nkoulou.
Bayal from ASSE is a solid, dependable CB.
I had both Lukaku and Neymar for my St. Ettienne team which won the CL in like the third season.
Out of the two, I'd say Neymar has more quality, scores more, but misses some absolute sitters, and a Neymar+Chamakh partnership would work better than an RVP Lukaku one imo.
No experience with Babacar.