Another Newbie

To answer your bike question, I'll ask another question:  do you already own special shoes for spin trainers at the gym?  If not, I'd suggest just using flat, regular pedals to race instead of purchasing extra gear you may not use much especially if you decide triathlon isn't your thing.  If you do already have the shoes and can afford the suggested pedals, go for it.  Being attached to the pedal is more efficient power-wise than using a flat pedal.  Down the road if you decide to continue doing triathlons, you'll likely want to upgrade to a road or tri bike at which point you can either keep using the same type of pedals or use more traditional road/tri pedals.

Best of luck to you, have fun out there!

Welcome to the sport!  

It sounds like you have other priorities than spending a ton of $$ on gear.  There's nothing wrong with that unless your livelihood is selling such gear.  

I have Rodeo pedals (Nashbar or Performance...can't remember which) which are platform (regular) on one side and SPD clipless on the other on my mountain bike.  

I have (gasp) SPD pedals on my tri bike.  A proper cyclist wouldn't be caught dead mixing mountain bike cleats with road gear, but they work for me (3 Ironman distance races).  I'm not so worried running through transition with my SPD cleats.  Plus, the SPD pedals are 2 sided, so I don't have to ever worry about flipping them over to clip in.  

Do you already have shoes with SPD cleats?  (Spin bikes usually use the SPD pedals).  If so, you're good to go.  If not, consider continuing with platform pedals and your running shoes (you could add straps or toe cages if you really want).  Running shoes are a lot more flexible and you'll lose a bit of power transfer, but you also won't be switching shoes between the bike and run.  In a sprint with a 15 mile ride, you'd probably not notice the 1 minute "slowdown"  riding in running shoes which is offset by about 30 seconds faster transition.  I did my first 2 tri's on a mountain bike with running shoes.