I think Korwin has pretty definitively answered on this, though you're right in that the rules for summoning and binding are particularly complicated. (Check out the how to bind link if you haven't already as it gives a few good examples)
To be honest I think the refresh amount and abilities for the demons needs to be decided between yourself and the GM. For instance Korwin's character had a particularly vicious magical crafter that would allow the PC access to powerful enchanted items without pay for the skills needed to use them which, if I were the GM, I wouldn't allow.
I'd personally limit the refresh of the demons you can summon to your own refresh, thinking that your character wouldn't have been given more powerful demon names than he could safely control (or perhaps I'd allow one extra powerful combat demon with a higher refresh, with the risk that he may escape his bindings and go on a rampage).
Really it's all about maximising your ability to summon, taking either ritual or sponsored magic and lots of refinements for extra item slots, then creating a focus item that allows you to cast complex spells straight away.