These first two are pretty much the same I believe but they are listed separately (where as green and black are listed together).
And the next one is 26", however I won’t one that is slightly versatile for other basic things. It’s also more expensive and as my first muni (I’ve been riding for around 1 and 1/2 years.)
These prices are all in NZD if your a bit confused.
As you can already ride I would suggest the 26er as it is that bit faster than the 24" and rolls over bumps better yet remains maneuverable, you also get a better range of tyres to chose from.
The Nimbus range is fantastic and bombproof, a bit heavier with the steel frame than a KH but no less as functional
You will love riding offroad and you will soon be trading up to a 29 or 36" MUni like everyone else 
Cool, I was also wondering how good the 26" would be for other things, nothing major but I’ve used my original uni to a point where the cranks broken and gets very loose. Things like one foot riding, hopping and some mounts.
THe newer unicyucles use a stronger crank interface so that is no longer an issue.
If you want to use your new Uni for trials and tricks the maybe a 24" would be better, Unicycles are always a compromise which is why people tend to have several for different activities. I have a 24" for jumping about doing trials/ big street etc, a 29 and a 36" MUnis for XC/road riding.
A 24" will let you go offroad and for many years was what everybody road, but it is slow and the smaller wheel is effected by bumps more, a big wheel rolls over them more easily.
You need to decide what you will be doing more of. you may want to get a 24" to do your tricks and experience the joys of MUni then when you get hooked (which you will :p) get a bigger wheel (29") for offroad and keep your 24" for trials/tricks etc.
One Uni is never enough (I have gone through 6 in a year of riding :p)
Hope that helps
Yes, I want to eventually buy a proper muni and a proper trials/street so maybe with a 24" I can get some of both to keep me busy. Also kinda random but do you think orange green or black?
For what you want to use it for the 24 seems like a safe bet and even if you got a 26 now I am sure you would want a 29er anyway.
Colour is a personnel thing but I have always liked that Orange and I was going to buy that as my first one but got a bit enthusiastic and bought a KH
I’ve decided that orange looks best! Thanks for your help.
Hello saeas!
I’d take the special offer, orange muni plus Kris Holms latest book. It’s a good read and has plenty of very instructive and inspirational pictures in it.
Greetings
Byc
+1 on the 24. Probably the most versatile uni. You can do some tricks and muni. If I had to choose one uni it would be a good old 24, though be aware of the tire size. You can find a lot more tires in the 26.
The 24 is more versatile. The 24 really isn’t ideal for trials and a lot of tricks but you can most likely manage. I’ve ridden 24 and 26 muni and the 24 is slower, but I feel more in control with it and can do more technical muni with it, and the 26 is faster, slightly more fun, and rolls over things easier.
I’m not intending to do hardcore trials on it, just the odd one footed and jumping up/down things
For your Orange 24 possible upgrade :
Brake
Lighter tire (Swable big betty 
change everything!)
Shorter crank in the 130-140mm range
My first muni was a 26 then I haded a 24… Don’t want anything bigger…
yes you do yes you do
spend spend spend
I ride the Betty and it is a top tyre, and Kris Holms book is a very good idea to buy as well
~ As to others have said… 24 is better for more tech terrain, less fitness, less skill, trials on side of trail, and climbing. Tech is relative, what is fun XC for one is knarly Muni to another. Also dependent on your terrain, what is legal expert trails here would prob barely be intermediate in north shore Vancouver.
If you want to ride as much as possible right away, I’d get a 24. As your fitness (uni specific) and skill increase you may want to move up. I’d get a used 24, & after a while, upgrade size and/or quality of the uni.