We are seasonal campers and love it. It seems that cinder blocks and wood under the tires has been covered. We keep our slides out all season, but don't be tempted to support them underneath b/c if the ground shifts or softens (which is inevitable) it can cause damage to the slides from too much pressure pushing up. Also, we keep the tires just touching and the stabilizers down.
Once you level, wait for the shifts and re-level. This will be inevitable since the ground will waver under the weight according to temperatures, melting, spring rain etc. Eventually it will level for good for the most part.
Could take a few re-levels for a year.
We connect our sewer using PVC and always remember to keep it at an angle down to the sewer...it's not like at home, it works by gravity.
Get a water pressure valve so you never have too much water pressure build up...got ours at an RV store, not expensive.
Get a surge protector that will detect highs and lows and avoid spikes or low surges to protect your appliances, etc. (This is recommended for travelers too).
As far as structures like decks and sheds go, find out the rules there.
We cannot put in anything permanent, so built our deck on cement pillars which hold 4 x 4 posts for that purpose.
Depending how elaborate you get, setting up deck, shed, etc. is a bit of work. But once it's done, it's less in the long run.
: People at your campground will be super happy to help you.
Our CG will offer workers to guide you. Mostly, fellow campers will help you!
Best regard and hope to hear of your progress and see pics too!