How to up workflow/editing speed

I have a MacBook Pro with a 2.3 GHz Intel Core i5 & 8GB memory w/ 80 GB left of storage (system takes up a a lot). Whenever I use After Effects, it takes a hell of a long time to playback things, sometimes crashes, freezes, etc. It heavily messes up with workflow/motivation. I'll have my resolution on, at most, a third and tend to use mostly photos, some clips, and shape layers. I'm not extremely heavy on effects other than things like glow, s_blurmocurves, etc.. Is there anyway for me to fix this? & which SSD would help if possible?