Just Some Advice
Try to be unique. All you ever see are those DotAs and Mauls, and it gets boring fast. Frankly, I find the best maps to be those little ones you have to really look out for like Swords & Armor, Murder at the Mansion, Dodgeball, Farmers & Hunters. Try to think of something nobody's though of, or at least take an overdone map and have it be a unique spin-off (like Farmers & Hunters to Sheep Tag). I know it sounds hard (and a little hypocritical, as my current map is a hero arena).
Just keep practicing. You dont really ever have to complete a map, just get used to what you should learn. And don't rush things. It took me about 5 maps to know everything and what triggers to use. But you can still create a great map with limited knowledge. And you can go back and fix it when you know arrays and custom models and what not.
Melees let you get used to the phyiscal map editing, while Sheep Tags and TDs have simple triggers and let you practice custom units (personally I still dont know good damage fields for those). DotAs, Hero Arenas are more tigger heavy, but can still avoid some harder trigger stuff such as Arrays and Variables. Epic RRGs and Campagins require more knowledge of Triggers and Camera movement. Custom Models help any map, but are work to make yourself. Also, you can always make things easier by just ripping code from other maps, although still try having the rest diffrent. And although I self taught myslef, you can learn how triggers work from other maps and by posting on these boards.
