Don't get too hung up on "Marine Grade" wire or anything. Just make sure it is good quality and tinned. It is hard to beat the prices on wire and stuff at genuinedeals.com or something like that for wire. They do have "marine" wire.
When crimping on steak-ons I always squit some corrosion resistant paste in before crimping.
At my job the last few years we have been using this product ....
Cortec ECO238 | VCI Cleaners have started using it on the boat too to spray the backside of electrical switch panels. This also comes in an emitting cup if you have an enclosed electrical space. This really helps with corrosion resistance over time.
If your renewing battery cables I would suggest the solder type lugs and shrinkwrap as opposed to big crimped lugs. Less corrosion issues over time.