To expand on what Mrs Flynn said, see if you can find a refurbished laptop. You absolutely need at LEAST an i5 CPU and a dedicated graphics card. For example, my laptop is pretty old (2012 model) and it can run Sims 3 on High (i5-2430 2.3ghz Dual-Core CPU, Radeon 6650M Graphics Card with 2GB RAM, 256GB SSD, 8GB RAM).
An SSD is absolutely necessary IMO. I'm using all expansions and all but 1 of the stuff packs. Cuts down loading times a LOT.