Some second hand gear can be a bit knackered - depending on what you're after, and if you're on a budget, some new gear is accessible. For clothing, Try Decathlon, or better still startfitness.co.uk and their brand Moremile - decent run, bike and tri gear. Prices are about £5 for shorts, £5 for tops, £30 tri suits, etc. they also do lots of reduced price run shoes.
Have a look at goinggoingbike auction site for bikes, other than that ebay is the way!
I'm riding my 26 year old steel framed "racer" with non-indexed gears on the down tube.
It is the best I can do on our budget at the moment. Got some 2nd hand clipless pedals and shoes of ebay (total £20), got a £5 track pump and pumped the tyres up proper hard, and sorted the wheels out so they are true and no loose spokes. Didn't half improve the ride!
Still was the worst bike by miles at the Weymouth tri, but I had fun anyway!
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