Memory Upgrade for fast video editing?

[Monkingme]

Hi folks, i love to do video editing with adobe premiere, but as videos are recorded more often in HD even from my smartphone i feel like there is not enough power anymore.

My system is Biostar Hi-Fi A55S3 Ver. 6.1 motherboard with AMD A55 Chipset, AMD 100W processor support
Now i am wondering if a memory upgrade to 8 GB would really make sense in that case? Or could it be a too slow CPU?

my budget is 300$, please help me and i will be seeking your advice. Thanks a lot guys!