Hello and welcome! The MS150 is a great ride and you will have fun doing it.
Now to answer your questions... what do you need?
jersey's - Get one. If you look on the internet, you can get one cheap. I always go to the Primal Wear factory outlet online. I have never paid over $35 for a snazzy looking jersey.
padded shorts - These are a must. Don't skimp here. I really like the Pearl Izumi Sugar Shorts- only $45 a pair and they have serious padding.
special socks - Buy one pair at $10, done. But they aren't a must.
shoes- Needed if you are going to go for clipless pedals.
hydration packs- Get a Polar water bottle. It keeps water cold for a long time, and there will be enough rest stops that you can fill up often. Camelbak's are great though, as you don't have to reach for a water bottle while riding.
proper sunglasses - I wear some glasses I bought for $10 at Target. They work just fine.
spare tire and a portable pump - You need a spare tube, somem CO2's and a bag to put it in that fits under your seat. A portable pump is not a must. Total cost- $25-$30.
I would like to have a trainer for days I just can't get out too - This is a huge cost. Honestly, if you can get a sitter... you need to get outside and ride. The time spent on the trainer is not the same as time spent riding outdoors.
Good luck!
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"