My biggest piece of advice is this, find an event and make a commitment to train for it and do it! A full Ironman (2.4mi Swim, 112mi Bike, 26.2mi Run) may be a little long for a first triathlon, but some have done it& there are many more shorter triathlons out there.
Id go to
www.active.com and find an event nearby that gives you enough time to train for it. Give your self about 12-15 weeks for a sprint distance triathlon and up to a year for a full Ironman. There is a lot of gear out there for triathlons; all you really need is a good pair of running shoes, a good bike, helmet, and a pair of bike shorts, swim goggles and swimsuit. You could spend a little more and get a pair of tri-shorts (worth the money) and a heart rate monitor. Dont spend too much money until you have done your first one, youll have a better idea how you want to spend it!
Find a good bike shop that is willing to work with you and fit you to your bike, give them your spending limit and let them know that you want to spend X amount and be ready to ride& bike, helmet, shoes, pedals, tool/repair kit, tax everything! A good bike shop will work with you, but be prepared to pay what the tag says, there is little markup on cycling products. You may save some money shopping online, but the service a good bike shop can provide is priceless to a new rider. At the shop, ask about bike maintenance class (many shops offer them for free, or will show you the basics before you leave) and if there are any beginner group rides nearby. YOU DONT NEED A $5000 BIKE TO DO TRIATHLONS! They are very nice but start small, upgrade as you get more involved.
Id look for a local triathlon club. I have yet to find a Tri-Club that hasnt welcomed beginners and went out of their way to help them prepare for their first event. When I started racing (in 1989) I was in high school and had no idea what I was doing, I was a runner which helped, but was clueless about triathlons. I after stumbling through my first triathlon a local triathlete helped me out with some pointers& I won my age group at every event I participated in the next year! Tri-Clubs are a great resource with numerous experienced athletes!
You need to find a training program, there are hundreds out there. The best available (IMO) is from Carmichael Training Systems their Classic program is $39 a month and worth it if you are very serious. You could also find a program at
www.beginnertriathlete.com with programs costing $75 for 6 month to free, these dont come with a coach but they are better than nothing. It also would be a bad idea to grab a book or two, like Triathlon 101 by John Mora or The 12 Week Triathlete by Tom Holland. Active.com had a huge amount of information for beginners as well. Magazines like Triathlete and Inside Triathlon are good resources as well.
Be warned, Triathlons are addicting! If you prepare for it you will have fun! If you are serious about it, PM me and I'lll give you whatever information and help I can.