I think if you've never donated before, its best to start off with gold supporter. You'll get most of the perks and a 2nd residence to start building on, at only half the price. Thats what I ddi before eventually going up to diamond at one point.
Yeah, I agree with cddm, gold is the best option. You honestly don't need diamond. You get access to Utopia, you get a 2nd res, you get 700r per day without voting and you get all the other perks too. You also get access to new servers or features before they are released*. It's all for only half the price of diamond. If you just want a real cheap option to just hide from the live map, get res protection and some extra rupees, you only need Iron, but thats only really for wild dwellers. *Only happens on occasions.
That depends on your budget. For me the sweet spot is gold because you get an extra res and most perks... However I used to be able to put more money aside so I was diamond! I have never been iron because it just wasn't appealing to me... Not to say that its not right for you...
You can see all the features you can get from each supporter option here http://empireminecraft.com/upgrade/
I would suggest beginning with gold, if you feel you still want more upgrade to diamond when your gold subscription expires
Yeah I started off with gold at first, then went to diamond .. Just waiting a few more hours until my alts diamond expires, then I'm going to put this account on diamond because it has soo many perks. I would without a doubt recommend diamond if you want alot of res's quick
Try giving yourself a goal before you start donating, especially since you're on a tight budget. The perks are helpful, but honestly, they won't make you much happier on EMC unless you were already enjoying yourself. You can fit quite a lot on one residence - just put your storage and farms underground If you still want to buy a subscription, it just depends on what features you want. Map hide is definitely helpful if you're building anything big in the wild. Utopia is nice, since it has no fall damage, night time, or hunger damage, but it's not really necessary. And remember that if you get extra residences with gold/diamond and quite donating, you won't lose the res's unless you go derelict. Edit: you won't lose the res's unless you go derelict AND someone wants to buy them.
diamond is nice, but not much different from gold except for 2more res and more ruppies the rest of it really isnt game changing you can usually get a diamond to place and explode tnt for you if you ask and flying on utopia (though nice) doesent really make a difference. if you want just want res protection go iron i guess, aikar is working on fiddling with map hide so its availible to everyone so iron just for that isnt really worth it, id say sayve up two months of iron and go gold then downgrade