In my opinion, the true Gold Era of Dragon was about #98 to #200. Before that era, Dragon very much resembles a fanzine in its layout, art, and the very uneven quality of its articles. But by #98, Dragon has become one of, if not the premiere fantasy Magazine in the industry, with an unrivaled run of fantastic cover art that pales anything before or since. The articles in this era or the most professional and often the deepest of any era. The advice on running campaigns is assured and polished. Even the short stories are often pretty darn good. During this period, the size of the magazine is steadily increasing.
I choose #200 rather arbitrarily, in that it was the largest Dragon magazine ever published. I don't mean that its strictly the best Dragon published (it's not) or that after that quality markedly turns down (not obviously at least).
After about #225 though, the decline of Dragon begins to parallel the decline of TSR generally. Dragon becomes less and less worthwhile, until revived considerably by 3rd edition. However, it never again obtains the quality of the previous era.
