I am trying to get one filter in particular "wavelet decompose" because i have gotten it to show up on my menu bar in two sepearte placees but neither work. They get error messages. I have hear about this G'MIC plug in that has bunches of filters but don't know what it is or how to get it or what i need for it or if I will lose anything like presets and keyboard shortcuts or anyting like that or if it will look different and have stuff in different places. I don't knwo what a LINUX system is and i am on a Mac El Capitan. I would love any help anyone could give since I am having trouble with this issue for work. I have attached some photos. Thanks so much best!

Hello dlabo12. I'm running El Capitan 10.11.6 with Partha's McGimp 2.8.14 and G'MIC 1.6.5; it works great. I've "googled" the particular wavelet decomposition "script", downloaded and installed into my Gimps script folder - it shows up under Generic... There is no wavelet decomposition "plugin" for the Mac that I'm aware of.

Now to your question above, if you download the versions I've mentioned above, you'll be okay. However, there is a new McGimp/GMIC version (2.9) and if you download and install it - none of your plugins will work as the 2.9 version is experimental.

Hope this helps.

Hmm, why are you using script-fu version of Wavelet decompose? I did not even know something like that exists haha
Gmic is powerful set of filters, it´s like a small application inside Gimp itself. Often updated, I peep the site for new updates regularly.
Go to Gmic page and download the Mac version of the plugin.

http://gmic.eu/gimp.shtml

Put it where it needs to be, Gimp-2.8.app/Contents/Resources/lib/gimp/2.0/plug-ins/ right?

Now, this is IMPORTANT! Many of the plugins and scripts don´t work before You change permission rights of the file.
This is often the case on Mac especially, but Gmic should work out of the box.
Have not used Mac for couple years, used to change permissions with a small app called BatChMod.
They need to have execute rights. You can tick on read, write and execute to be sure.

https://www.macupdate.com/app/mac/6440/batchmod

Or alternately you can do it from terminal or simply from file menu, get info, sharing and permissions, privilege.
More here if that´s double dutch to you:

http://www.macinstruct.com/node/415

Also, which version of Mac Gimp You are using, I suspect the official 2.8.16 from gimp.com/downloads?
That could be revelant, as custom builds might miss some files that are in the official and some plugins don´t necessarily work.
At least I had that problem with some Windows custom builds.
Oh yes, don´t use any beta builds, like Dinasset mentioned. There are always compatibility issues with beta or major upgrade versions.

You could also try to set now the permissions for the wavelet decompose plug-in if You extracted it from the Partha´s build.
Can´t promise that it works
but wavelet decompose is somewhere in filters menu, Filters/generic or Filters/enhance.
They should be located usually in a logic place. (Gmic goes on bottom of Filters menu)

This is little more advanced but You can also change the place where plugins and scripts shows up in menu if you want, with a good text editor.

Hope this helped you bit forward at least. You´ll get there for sure, it´s always behind a small struggle when You start playing with new application.

Nidhogg, thank you for all the great information in your post! I do use BatChmod and ensure that when I use it I check enclosed folders as well.