For sps, I am no expert on, but you can search around for it and seeing what you can find. I found this post:
https://www.reddit.com/r/VRchatAvatars/comments/1gdwx7w/sps_help/
That seems helpful.

For clothing, it depends on what you want. If its simply adding it onto your model in Unity then...
This video will help with that along with the lattice tool: https://www.youtube.com/watch?v=aHFulMbnWwA
Tool: https://forum.ripper.store/topic/77591/gift-unityeditor拡張-非破壊ラティス変形ツール-lattice-deformation-tool?_=1768181765989
(The lattice tool is for Unity only, it helps with fitting the clothing on your model without using Blender)

If the link to the tool doesn't work, I have the tool downloaded and can send it to you myself.

If you want GoLoco here is where to get it, its completely free: https://franadavrc.gumroad.com/l/gogoloco
Here is a video to help you set it up. Don't worry, you will get use to it over time, this is WITH VRCFury: https://www.youtube.com/watch?v=pZ5W6PIrdRk

This one is without: https://www.youtube.com/watch?v=OeckPy_sGdM&list=PLnxM1fvb1YCX8AjfCBf5le0esKb6YiRly&index=7&t=305s

If you want the how to make clothing in Blender and how to weight them and fit them on your model, I can easily tell you / show you that at a later date.

No worries you good. Feel free to ask for more help. I wouldn't mind helping you find helpful videos or teach you myself. (Free of charge of course. I do NOT want your money)

Oh and if you want notifications for posts you posted or commented on, I suggest hitting the little bell icon in the middle between "Mark unread" and "Oldest to Newest".

That way you won't miss important things on the posts you want to keep an eye on. (Assuming you didn't know that)

Link: https://www.youtube.com/watch?v=bSwMz4WcajQ&list=PLt8qiEFqNHFkPqpKLnVRx-G78mGvjPbFt