Having worked on a few weekend cups both good (DreamHack/Lockdown Throwdown) and bad (Essentials Monthlies) there are a range of lessons I've picked up so I hope that these answers are helpful. Also speaking for myself only, not Essentials as a whole.
1. Right now any prize pool should try to reflect the effort teams would normally put into their respective leagues. I think in the range of $200-300 would be reasonable for smaller tournaments not relying on external sponsors, can be higher with signup fees but that comes with its own considerations.
2. Most of the tournaments I've been involved with has featured separate Invite and Open brackets, where the top teams from Open qualify for a playoffs with the Invite teams. This is mainly for two reasons:
- A) Matches in the invite bracket can be casted for good stream content for the audience and potential sponsors
- B) Takes the best players out of the open pool, making matches a bit fairer
Note: You could also use the rationale in point B to create a Newbie only group to take the lower skilled players out of the main tournament if you so wish.
3. Mirroring regional league formats tends to go over easiest, but I recommend that you do timelimit 30 with a 10-15 min golden cap if needed. Doing so gives you a strong estimate for the longest a single map/match can take.
4. Ask around. It isn't particularly difficult to get something decent with a few friends and someone learning the basics of producing (Camera Binds, When to switch POVs, Casting Essentials, etc.). Most of the more experienced people involved with producing or casting tend to be quite keen if they are free.
5. There are a range of systems (both through tournament systems or externally) that allow signup fees, I believe both Challonge and ChallengerMode both offer it but I cannot say for certain.
I'll finish this with some advice, the existence of leagues makes frequent weekend/2-day tournaments not particularly viable, as people will get burned out or uninterested fairly quickly. Its tough work making yourself stick out from the crowd and there's a lot to think about when it comes to organising. I wish you the best of luck if you decide to go ahead with it.