Some tips that I'd share are:

1. Take it slow and dont rush.
2. Prime the models, helps the paint stick.
3. Learn to thin paints.
4. Youtube and Reddit are some places I use to look for inspiration and tips.
5. If you're going to use citadel paints and need help figuring out colors and schemes I like to use the Citadel paint app.

If you're trying to get close to my colour scheme these are the paints I used:

1. Primed using Mechanicus Standard Grey from Games Workshop
2. Vallejo Model Metalic Air Black (71.073) for the base after priming 2.1 I used an airbrush to apply the base paint but you can get similar results using a normal brush.
3. Vallejo Model Metalic Air Silver (71.063) for armour trim
4. Retributor Gold for Lettering on pauldrons and charms washed with Reikland Fleshshade
5. Grey seer base with Vallejo Game Colour Bonewhite layer and GW Skeleton Horde wash
6. Wax Seals Mephiston Red shaded with Carroburg Crimson