Welcome!

I won't reiterate what's already been said- they are all VERY good suggestions.
I will say one thing. When I first started out I was overwhelmed with the price of things. I did almost all my shopping on e-bay and wound up with GREAT things for very cheap. I got my clipless Sidi shoes for $10, some jerseys for less than $10 each, some new cycling shorts for $30, and some sunglasses with interchangable lenses (the kind that won't shatter if I crash) for $20. I really found some good bargains, and it was winter (like it is now), so you can find some good deals on summer-ish items. I figured that I saved hundreds of dollars just by being vigilant on e-bay. Gotta love other people's used things.

Best of luck to you at the MS150!!! I hope you love biking as much as the rest of us here!