I was in my early years of working out, and I read all that stuff on how great HMB was. I was a little green about supplements also, and was going to buy some. The stuff was so expensive, I said, F' that.
A bit later I came across a store that had some HMB on sale, plus it was like the jumbo size bottle and within like 5 months of expiration. So I bought a big bottle of 120 caps at 500mg each for like $10... I bought a second one also.
I used it at 1g/day, up to like 4g/day, and that with whey were the only supps I was using, and honestly I think I put on some size quickly. I only used it for about a month or so then stopped. I went to use it again later on and found it did absolutely nothing. I have never tried it since.
I have read in a few more recent writings on HMB, that it may offer some help in recovery for 1st time weightlifters. Experienced weightlifters seem to have no positives from using it.
So all in all... much of the info on it is just the usual hype.
That's my story...