Welcome to the hobby. I too started with an elite army back in the day (Grey Knights in 3rd edition) to only have to paint a small force. Now I have about 15 armies across
40k and Fantasy.
1. Just get the
GW gold spray if you like the color, it's expensive but it'll save time and it's basically the same color as the gold from the pot, the same applies to Leadbelcher.
2. Expensive. Amazon has decent brush sets like these (
https://www.amazon.com/gp/product/B01M7UFLP5/ref=oh_aui_search_detailpage?ie=UTF8&psc=1) but
GW brushes are okay, they're just sold at premium prices like their $8 water pot.
3. No, unless you have bad eyes. I got one and it's buried in the basement somewhere.
4. Try a sepia, Reikland fleshshade, or agarax earthshade wash then add a highlight to that . Fleshshade makes a redder gold, earthshade makes a darker, dingier gold.
5. Using "washes" to add depth to the recesses. It's very low pigmented paint that runs into cracks, just don't go overboard with it. I like to thin the black wash with a little water or medium or it tends to clump around the bottom of edges. You can get the blue or green shades to actually tint silver armor and it makes a nice effect if you do it evenly.
6a. Watch the Warhammer TV painting videos on YouTube, Duncan breaks down painting into bite-sized steps. I've met him, nice guy. He paints Custodes here:
https://www.youtube.com/watch?v=dm8J-kaezWM
6b. Don't use your tiniest brushes for painting armor, cloth, or flags, you'll be there all bloody day. A medium-sized brush can do a lot.
6c. Paint the inner parts of models then work your way out. Ex: paint a guy's pants and shirt, then his skin, then his armor, then the cloak over the armor, then his sword and shield, etc. If you start doing outer parts first you'll have a lot of messes to clean up as your brushes go into deeper detail.
6d. Thin your paints with some water, watch the Warhammer TV videos and Duncan will show you this over and over and over.
6e. Practice colors and washes on bits of sprue before you toss them. That's also a good way to try new primers, here in Northern Virginia we go from 95F with swamplike humidity to below freezing so I use some bits of sprue to test the air with a rattle can before I spray all my models. If it doesn't go on smooth I don't spray that day (I sprayed about 1500 pts of Orks one day and they all came out like sandpaper because it was too humid).
6f. You can get a lot of bare plastic starter set models for cheap on eBay to practice painting before doing your actual models.
6g. Enjoy the hobby, it's great.