As I wrote befire, you need to watch tutorials how to implement all the assets and how to use them. And you also have a lot of free stuff on the internet. There is also a lot of pirated high quality stuff. If you use that, too, I would recommend to support the creators of these assets, if their assets will give you a benefit and if you will use them often. If think I would be only fair. But first, you should start with free content I think. Don´t give out money for things you will not use in the future.
Depending on the assets you will download, the download time and size will be very different. The more textures, the more MB/GB. Morphs, Poses are very small files with 1 - 10 MB. If you are motivated enough, you will find everything you want and start to do what you want. Furthermore, you should check the F95 forum. There is a lot of stuff, too.
And there are many devs and experts who give you advices and can help you with different problems. But I would recommend you to try out a lot by your own. And make the first steps before you contact someone with a difficult problem. Many devs dont have the time to explain you every little detail. This is something you need to consider. But again, if you show some potential, you will get support, from devs and from followers.