I have one coal mine and one ore mine, I don't think I have space for more *shrug*
Well, depending on how long you want to play your city, your long term goals would be to unlock alloy smelting with your first upgrade, then unlock the oil division of trade ports with the next upgrade. Then use the trade upgrade that you should have gotten in the meantime to upgrade the oil division of the trade port. Then use those upgrades to get a head start on Electronics, since you need both plastic and alloy, and having a trade port that can do both is space efficient.
Or, you can just import coal and ore when you run out, and just keep doing alloy, since that also makes a decent profit.
The downside of both electronics and alloy production, though, are that they produce a shit ton of pollution.
I haven't played the game in a while since 2.0 came out, (been playing Civ 5 instead), but in my last several games, I've done nothing but commercial and residential to keep the pollution at zero. Or, near zero, if I put in a couple high density industrial to provide jobs to balance things out.
They need to completely rethink the game design and philosophy regarding trade specializations. After a lot of thought and gametime tinkering with it, the implementation of it seems completely wrong to me.
Anyway, here's an example of the kinds of cities I was making before I kinda stopped playing the game.
http://www.neogaf.com/forum/showthread.php?p=54030222&highlight=#post54030222
edit: You know, it's kinda sad that after you pass 500k population, the game music changes to a really cool variation, but hardly anyone is gonna hear it since getting to 500k pop without getting completely fucked in the process is kinda hard. And not in the "ooh this is awesome challenging gameplay" ideal archetype of "hard". Well...it kinda is for
me, since I'm a glutton for punishment. I guess that's why I liked God Hand so much