I experienced gynaecomastia when I was 19, I think in part as a response to starting to lift weights and eat more as well as probably some late pubertal development.
It was only on the left side, and was very sensitive. Doctor was of course very little help and decided to put me through a breast cancer screening, so I took matters into my own hands by getting my hands on some Tamoxifen (Nolvadex). I dosed it at 20mg ED for 2 weeks, it resolved itself by day 9 and never came back.
Tamoxifen has a slightly better reputation than clomid as far as SERMs are concerned, but I'm aware of the fact it's considered to be hepatotoxic amongst other side effects. Either way, it's been years since and I've not had an issue of it's kind again, and I think the cost and time investment is low enough to consider it in cases of pubertal-associated gyno, especially when it's a recent development.