Optimizing my system for Adobe Illustrator

Hi,

I have tried to find some helpful information about this topic by myself, but there's so much to find that I kind of got lost in all this information.

So here's the case: I like Illustrating things in Adobe Illustrator and apply a finishing touch in Adobe Photoshop. I also like photography and from time to time I use Lightroom to edit some RAW images, but Illustrator is the program I use the most. By far.

This works nicely, but I have a few problems. First, when I have placed a lot of brush strokes in Adobe Illustrator in a single layer, it tends to get slow. The more brush strokes, the slower it gets. This is especially a problem when illustrating hair, for example. The zooming gets slower as well. As soon as I start editing in another layer it's fine again. Also, when editing big files in Photoshop it tends to get slower.

So I want to optimize my Illustrator experience. These are my current specs:

Motherboard:  MSI H97M-G43

Processor:  Intel Core i5 4690

RAM: 16GB

Power supply: Seasonic S12II 430 Watt

256GB SSD

1TB HDD

As you can see, I don't have a graphics card. I was looking into purchasing one, but I have no idea which one would be overkill and which one would suit my system. Also, I am kind of on a budget. So I was looking into buying a second hand graphics card like a GTX 760 or GTX N750Ti. Would that be better? Or should I upgrade my RAM to 32GB first, or maybe do both? My budget is about €200, but the less the better.

I do not game and only do 2D editing. I am not planning on doing anything 3D in the near future. I am also not in video editing, except from the occasional holiday video which right now is going fine. All my Photoshop/Illustrator files are, while editing, stored on the SSD.

Thank you very much!