The first things you should know about triggers are:
- Can I create them at all?
- Can I make them efficient?
- Can I make them leakless?
All these things should be answered with "yes", otherwise you need to read a tutorial about that topic.
The first trigger you should make is the init-trigger, there will be 1 and only 1 trigger with as event "Map Initialization".
After that, create the hero-choose-trigger (this should be only 1 trigger when it's efficient).
Now you can think of some other necessary things: a revival-system, for example.
Of course, this will be the basic of the map - nothing special here.
If you cannot create these things like I have mentioned (efficient and leakless), read some tutorials!