Almost all mods can be made in just XML (aka tuning), and is where you should focus first before venturing to scripting. You also don't need to do scripting majority of the time due to community tools that handle injecting for you, it's only when you require stuff that isn't covered.

You don't need any skills unless you want to do scripting, and even then Python is easy enough to learn with outside resources, it's just that transferring that knowledge to Sims 4 is what's hard as it's not well documented.