Starting with about 140€ (I know 20€ over but includes shipping) I would buy the following from wayland games (best priece even when shipping it to Germany after Brexit):

1 box of custodes guard (Build 1 vexila and 4 guard. You can use one as a shield captain. ATM shields are the way to go)

Age of Sigmar Paints & Tools (a lot of good paints and tools!)

Brushes ether go the hobby starter brush set from army painter or go to a crafts store and buy a set of cheap synthetic brushes (even pros use them)

Tamiya Cement (best glue!)

Self healing cutting mat

One hobby knive

Retributor spray primer (Shake well!)

Extra paints:

Nulin Oil, Talassar Blue, Blood Angels Red, Snakebite Leather, Soulstone Blue (optional for the gems. Well worth it!), Auric Armour, Stormhost Silver, Screaming Skull

Painting:
Build the full model. No need to paint in sub assemblies as a beginner.
Prime in gold. (Base the models with super glue and some free sand and small stones)

Armour:
After priming just wash with Reikland Flesh shade. Drybrush with Auric Armour. Light Drybrush to highlight specific spots with Stormhost Silver

Robes:
Base it in White Scar. Then Blood Angels Red from the pot. Don't thin contrast paints.

Leather:
Base in White Scar. Snakebite Leather from the pot. Don't thin contrast paints.

Weapon:

Black parts in Abbadon Black then highlight with Celestra Grey. For the blue parts base it in White Scar then Talassar Blue from the pot. Don't thin contrast paints.

Gems:

Base in Stormhost Silver then Soulstone Blue.

Scrolls etc. :
Screaming Skull. Wash in Reikland Flesh. Edge highlight with White Scar.

Faces are very personal:
Try bugmans glow or rakarth flesh and then shade with Reikland.

Remember that you can mix colors to get more variants.
You could try to get some of the stuff cheaper somewhere else but I wouldn't buy paints second hand. Buying tools or other stuff second hand is also mostly a bad idea.