I basically have 2 questions within this.
1. Is this worth even starting? So far it seems expensive but the only army I would make is Necrons.
2. If I start, what box models should I get? Imotekh is my favorite HQ but i dont want to spend 20$ on it if it is a piece of junk. So, which box models should I buy for a good army and how many of each set? I’ve seen that Monolith building thing and was wondering if it is normal in a Necron army, so please list every set I would need for an army.
Please see my reply to your previous question on whether you should start or not.
In terms of what models you should get, it’s impossible for anyone to tell you really. Your best bet would be to get yourself the Necron Codex and look through the different units. You can then decide what you think suits you the most.
You can also head over to the Dakka Dakka forums and read through some of the necron posts to get an idea of good lists. However i’d recommend going for models you like the look/playstyle of initially over a purely competitive list as this can often sap the enjoyment out of the game if you’re playing a force that you just don’t enjoy.