This is such a subjective topic. So many factors that can apply to a person individually. Lots of great insight though.
So, I will offer my insight as to why I chose my various options (that is still in shipping status, undelivered, so take this all with a grain of salt).
All IMHO:
1) Advanced Safety Group - was a must for me. My tacoma TRD pro had Adaptive Cruise control. My current 21 rebel does not have it. I hate not having it. It actually makes cruise control worth using....and works beautifully.
2) Bed Utility Group - was a must for me. I like having a bed liner, so I would have put one on anyway. For the price, this liner accompanied with the track system seemed a no-brainer as the cost was pretty much in-line with aftermarket.
3) Carbon Fiber - not worth the $1300 for me. I like the plain black interior. That is just me though. This seemed an obvious cost savings. Again, for me.
4) Engine Block Heater. For the price, it seemed reasonable to have living in an area that gets cold winters. Not too expensive to deter me. Priced well enough.
5) Standard Wheels. I went for the cheaper wheels, knowing that I like 20" wheels and will therefore eventually replace them.
6) Decals - I don't care for them. This was an easy pass for me.
7) Rambar - I kept going back and forth. But I like my carwash. It's part of my routine. Easy way to keep my truck looking nice. A RAMBAR with lights would have put an end to this. Plus, I do more urban/suburban driving. This can always be added, and easily.
8) Red accents - Easy pass for me. I am not a fan of red. I like my interior black. This is just me.
9) Tow mirrors - I love them. I also tow stuff. I also think it makes the truck look like the truck it should. A difficult retrofit as I understand it...so if you don't get them, you may be a bit screwed to add it at a later date.
10) Running boards. I like them. I have women and children in my life. I also like the look of the off-road ones. So, this was an easy choice for me. That said, if you are unsure, you can always add them later.
11) Tonneau cover - I don't like soft covers. This was an easy pass. The sky is the limit with these, you can always add one. I love the gator trax hard cover I have on my rebel, and will port it over.
12) LEVEL 2 - gives you so many things. Pass this one up and you could have major regrets. I get that many people don't want to pay the money and are perfectly happy with level 1.... But if you are accustomed to any of these features, then it is an no-brainer....was for me. Plus, gives you HK etc...
13) Skyroof - I got it. But honestly, I might not again. I just don't think I need it. I guess it is nice. My current rebel has it. It SEEMS nice. But I just don't use it. That said, a retrofit would be....well, is that even possible lol?
14) Trailer reverse - I have no use for it. I tow lots of stuff, but they are on standard trailers. I have no use for tow reverse cameras etc. This is just me. All I need is a trailer brake control which comes with the LEVEL 2. I also want all my aux switches.
15) Tire carrier - I use the truck to haul stuff. I like having a bed to do this. I live in the suburbs. I have no use for 2 extra tires in my bed and I don't off-road in Baja. This was an easy pass for me.
Hope this helps.