Gear

Anything that fits.

Lightweight - fabric will probably do (but you may want leather).  I did the three peaks last year in a pair of second hand Regatta's I bought for £5.

Do you mean the National 3 Peaks (Ben Nevis etc) or the Yorkshire 3 Peaks (Whernside etc.)?

If National, it depends on whether you are trying to do it in 24 hours & whether you will be running any of it. I did quite a bit of running (on the flat & down) when I did it, so used a pair of running shoes. Otherwise any comfy fabric boots should be fine. I assume you will be following pretty traditional routes up, which are pretty good paths.

If Yorkshire, some bits are quite boggy, so you may want to get some with a waterproof membrane inside. However, remember if it goes over the top your foot will still get wet & then it will be difficult for the water to get out. Gaiters could help with this.

I should say I walked up from Wasdale (yes, be quiet as likely to be there pretty early in the day!).

That path is pretty dry, don't know what the Corridor Route is like underfoot.