Getting started with off camera speedlite (5DM3/600EX-RT)

I want to mount a 600EX-RT on a light stand with an umbrella, and use the 5DM3 wirelessly.

1. What is the least expensive, quality transmitter to get to go wireless? I will also be using Hensel lights at some point, and I'd like to find a transmitter that, if possible, will work with those as well.

2. I'm trying to attach a hot shoe to the light stand so I can connect the speedlite. Does the one in the attached photo look right? The problem is it does not seem to tighten correctly. When I turn it and it tightens it is at an angle and is no longer pointing directly into the umbrella. What am I doing wrong?

Thanks.

I haven't used hot shoe flashes for a while but at the time http://www.flashzebra.​com/ was a nice site. You need to get an umbrella adapter which will come with hot shoe also. For triggers, simple pocket wizard plus IIs still work like a charm after 10+ yrs.

Having a Canon 5D Mark III and a Canon 600 EX-RT needs to have the Canon ST-E3 RT Transmitter to complete the ride. Off camera Radio Transmission, E-TTL and Manual, Group Mode availability when you purchase a second 600 or more, and you will. Plus the most reliable seamless connection. No third party "Variables" to worry about. Also you have full access to features and controls from the Transmitter on the camera hot shoe. No need to go back anf forth to light stand to camera and again. This again will come in handy if you should go for additional 600's.
Going the cheaper route is like buying a Porshe and putting in cheap gas. Top Performance.
As far as an umbrella holder that the 600 sits nicely and secure is the Westcott umbrella adaptor with Cold shoe.
Comes in a kit with a Westcott Apollo or sold separately.

https://www.bhphotovid​eo.com …78402%2C&is=REG​&A=details

I'm thinking about starting the migration to the 600 but I'll keep my pw ittl and plus? Radios as I use elinchrom quadra lights also for times when the speedlight will not cut it. When I get four or five of the 600s if the setup uses exclusively the 600 then I'll use the canon radio system if not I'll use the pw radios. Be nice if they would work together.

I also have a couple pocket Wizard Plus II's and III's for my older Profoto Compact 300's. The Profoto's have built in PW communication. The PW's are for the camera hot shoe.
Different tools for different jobs.