You don't need a Gold Subscription to do ANY of that.

You can make levels and put them here for review. A lot of developers are here, iClassic and iEra. iZone, iKingdoms, etc. The best thing to do is practice practice practice and have one of these supported servers pick you up, because you'll be given a gold subscription (instead of wasting money on one).

On the contrary to popular belief, buying a server is a terrible idea. I can't tell you the last time I saw a successful emergence of a private hosted server move to a classic hosted server via PC. It's sad to see people drop a lot of money into a server, to just give it to someone else to just "screw around". If you want practice, you can request access to the Testbed server to practice scripting and leveling for FREE.

If you decide to attempt the "make my own server" route, plan to put aside at least 2 years in development with a rotating crew - don't expect people to stick around, because they generally won't. I find that most private server staff have, on average, staff access to at least two other private servers where they dedicate time and focus to, lessening the content you get for your money pit in lieu of someone elses' money pit.

tl;dr: Don't buy gold subscription specifically so you can 'make levels'.