The extra paid plugins are definitely NOT necessary to get a lot out of redguides. I got through entire expansions worth of content with just
RGMercs specifically trying to find its limitations and it's better than the last time I used it. I primarily used
KissAssist which was the main selling point of level 2 access when I first came to redguides. I never spent a penny on paid plugins and was extremely happy with RG as a whole. My only regret was not starting years earlier.
For just getting started,
RGMercs is pretty great with a very low bar for entry as far as knowledge goes. You need to know almost nothing more than how to turn it off and on and set up a camp to get a ton of mileage out of it. (A bit more than that would be ideal but isn't strictly necessary). It's not as customizable as
KissAssist is, but it's really quite good right out of the box
KissAssist requires a bit more setup, but is extremely powerful for its relative simplicity. There's also the
KissAssist library where you could just take a working ini someone else has already written and be off and running in a few minutes. The ini library is also a great way to dip your toe into writing your own ini's without starting from scratch. Up until the day I quit playing, my enchanter ini outplayed me playing by hand by some margin and all I did was start with an existing ini and then as soon as I found behavior in it I didn't like I'd try to fix that one problem. Then repeat that again and again until I can't find any problems. In doing that, I learned a little bit at a time and ended up being able to write my own from scratch pretty quickly.
A note unrelated to that specifically. You can keep your level 2 access with redcents. Use your 4 redcent reacts every day (on comments that are worthy of receiving it) and you can maintain level 2 indefinitely on that alone (you receive 1 redcent each time you redcent react someone else). And if you contribute to the forums you're bound to pick up some redcent reacts of your own which earns you even more redcents to spend on level 2 access.