i need help to properly clean the guitar

Depends on the finish, but when in doubt a soft damp cloth will get the job done.
You can buy guitar polish, you can use these if your guitar has a gloss finish, don’t use it on a matte finish.
A soft bristled brush can be used to get at the dust in the hard to reach places around the bridge, etc.
For the fretboard, if it’s maple, it will have a finish on top, guitar polish will work fine. If it is rosewood or ebony, a damp cloth (not wet), be sure to wipe up any excess water, one or twice a year treat with a touch of oil.

Little bit oiling the tune heads and …..just 2-3 drops on the fret board (not more)..then gently rub it with dry cloth

https://syngates.com/forums/topic/best-way-to-clean-guitar-neck/ papa gates gave some useful tips

Here’s the rundown of what I do every other months or so (it’s extensive and I’m a perfectionist about it)
1. Get all the dust out of everywhere. I use canned compressed air from Best Buy for this (usually used to clean computer keyboards).
2. Use a microfiber cloth (phone screen cleaning cloth) to clean everything out of fingerprints and dust specifically
3. I use Kyser Lem-Oil to clean and treat my fretboard. Spray it on a cloth, rub each fret down, use a dry cloth to polish.
4. Adjust action/neck (if needed).
5. Restring and retune
Once a year I also use this product called Frine on all my frets. The stuff’s a damn miracle worker. De-oxidizes and polishes frets. Makes a cheap crappy fretboard feel premium. Can’t recommend it enough, I think it’s carried in most Guitar Centers.
The Kyser Lem-Oil is basically lemon oil mixed with other stuff that’s good for a fretboard to be cleaned with. You can clean it with water, but use a damp rag and not a wet one, as too much water can be bad for the wood.

How would you get rid of gunge build up, I have pretty corrosive sweat and fret board has a build up of rust and gunge?

A small piece of plastic, like a credit card, can be used to scrape the gunk away. For rust, cover your pickups and mask either side of the frets with painters tape, use the finest grade steel wool you can find to polish the frets.
There are plenty of youtube videos if you are unsure.

Cheers dude!