The term bottleneck doesn't have much meaning when you are talking about a Core i5/i7 1st gen laptop with 4GB of RAM.
It's hard to make a GPU recommendation as you haven't given us neither a budget nor what you are trying to do or play with this new graphics card. If I was told I had to turn this into a laptop that could play light current games I would get the EXP GDC, and RX 460 or GTX 1050 or GT 1030 (cheapest), an SSD if it doesn't have one, and a 2x4GB RAM kit. The bottleneck wouldn't be that bad for the GPU. The CPU is your limiting factor in all cases.
Or save yourself the trouble and get a new laptop.