Replace to new PC or upgrade current one

Hi, im really not knowledgeable or educated at all things PC parts related, but im slowly learning. I want to improve my gaming experience a bit and i think it might be smarter to just buy a new pc instead of replacing my CPU and GPU as it seems like my motherboard is really old
heres what i got:

Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz 3.60 GHz

RAM ‏‏‎16.0 GB

233 GB SSD Samsung SSD 960 EVO 250GB, 932 GB HDD WDC WD1003FZEX-00K3CA0

NVIDIA GeForce GTX 1070 (8 GB)

what do you think? also, if lets say i just buy a new PC, what do i do with the old one? any parts of it are woth saving? maybe selling?

thanks!