OP, make sure to understand the difference between Genie+ and Individual
Lightning Lane (ILL$). They are two separate things even though they seem like they're connected since you end up in the Lightning Lane (LL) no matter which thing you book.
You do NOT need to purchase G+ in order to purchase ILL$.
ILL$ are available for the top headliners in each park--FOP at DAK, RotR at DHS, Remy at Epcot, and 7DMT at MK. This is true until August 7th, when some other attractions may revert to be ILL$.
If you want to ride any or all of these rides without waiting in a long line or either being at the front of the line at RD and making a dash for it or waiting until near park close and hoping the ride is still up and running, then you should buy an ILL$. Yes, I'd prefer not to pay for this, but it is worth it, since the lines for these rides can be epic.
If you're staying onsite, you can purchase an ILL$ at 7 a.m. Yes,
MDE has major glitches when it comes to booking these. I've been kicked out while it was processing my payment. And make sure you know your Disney login, because they will ask for it. You get your choice of times, sort of, but by the time you book, the time you selected may have been changed. If it's an attraction on your must-do list, then take whatever they give you and work out the rest of your day around that.
Certainly none of this makes planning easy. And if you fail to get the ILL$ and/or G+s you want, you can't easily change your park reservation.
I don't like this system, but it is workable, depending on what you want to use it for and how much you're willing to spend. Or, otoh, how long a line you're willing to stand in for any ride.
We use G+ at DAK to ride the safari twice--once at RD and once with G+--and for NRJ. Sometimes this doesn't work out, since NRJ might not be available for a time that works out for us. We've learned to go with the flow and not mind (too much!) if we paid for G+ and got only 1 ride out of it. We think of it as ILL$-minus.
The people who seem to be getting the most out of G+ are people who stay in their reserved park from open until close and are willing to crisscross the park and ride pretty much anything that shows up in G+. This works very well at MK.
Only you can figure out if it's worth it for you. And if you do decide to use G+ and/or ILL$, please read up on both of these before your trip. There's strategizing involved. A lot of strategizing.
ETA: G+ can also work well if you book G+ attractions for the late afternoon or evening and stack them during the day. This requires not just strategizing but also diligence, since you need to book everything at 2-hour intervals and spend a lot of time refreshing your MDE in order to get times you want.
Yeah, I'm not a fan but I have learned how to work the system a bit.