How should I upgrade my Omen 870-219

[snowy_]

I bought this pc 3 years ago and have served me greatly but I believe that its due for an upgrade. I'm not sure whats more important or the if these are the only things that I should be looking at but the three things i see fit to change is the 1tb of hhd to an ssd storage, upgrading my 12 gigs of 2133mhz ram (i have no idea why its 12 gigs), and upgrading my graphics card. 

The specs of my pc currently is :

cpu: i7-7700

gpu: gtx 1060 3 gig

ram: 12 gigs 2133mhz

memory: 128gig ssd and 1tb hdd

also im quite sure that i have to upgrade my mother board if i want faster ram or if i want to upgrade to 2x16 gig sticks instead of 2x8. I don't know if i need an upgrade to my power supply either because my pc frequently has a problem of disconnecting and reconnecting usbs. im 99% certain that this is a problem with the pc because almost all of my usb input devices have had this problem and right now my webcam has never worked and constantly went from not being detected to being detected upon trying to turn it on. 

[Prométhée]

Hello
ok, but what exactly do you want to know?
for certain points that you indicate, it is simply up to you!
You talk about replacing the motherboard, if you get there then your best bet is to move on completely
You may have difficulty, to adapt another motherboard, in the HP box
the Hp box may no longer be suitable, and / where, it will not be suitable for good cooling
Basically, you change the motherboard,, memory module, better graphics card, more powerful power supply module, finally you change computer.