Roxton's Simple Tips
Important Starting Tips
1) Unless you know exactly what you're doing, research unitless at <=1.7k land. For best performance, make a geld buffer of ~50 million, and then destroy all towns/farms/nodes. (If you have heroes, some nodes and a bigger geld buffer will be required.)
2) Especially in the mid-game, 2k land is too dangerous to make significant headway by attacking. Use Nature's Lore to explore to 3.5k in order to dramatically reduce the number of attacks on your mage. Mono-nix with missile shield and wooden soul is a great turtle stack for exploring. Bonus: 3.5k land gives you enough geld to buy expensive defensive items.
(Let me reiterate that. All you people wallowing in 2.5k land, the reason you can't climb isn't that you suck. It's that 2.5k land is a bad place to climb from. So don't lose hope.)
Secondary Tips
3) Yes, your biggest concern is chims. Avoid putting treefolk in your second stack. Nix second stack handles chims nicely.
4) Treant is an all around awesome topstack. RDs won't do enough damage. Nobody will, except flamebladed greens (and maybe topstacked chims, but that's uncommon). To defend against FB you need barriers, or you can take your chances with carpet.
5) Conventional wisdom says to leave some complexes and ultimates while you MP charge. Conventional wisdom is wrong. A simple analysis shows that, until you reach very high land, the number of turns it takes to summon a complex/ultimate unit is much smaller than the number of turns it takes to MP charge that unit's upkeep, so for God's sake, disband all those trees. Off-color is the exception -- don't disband efreeti.
6) Green lends itself to short-stacking. Pad out your remaining slots with very small fatigue stacks. EM/EA/Druid/Archer are nice recruitable fatigue, with Dryad/Nymph/SS/PW/Efreeti as possible fatigue summons.
7) Some of the barracks units are worth looking at -- elven magicians and swanmay in particular. I avoid them, however, because I like money.
8) Last but not least, try to keep your power high to dissuade attackers. This is a particularly high (and difficult!) priority for mages with barriers. You don't want to get attacked more than twice. The three tools to achieve high power are 1) Barracks units, 2) Low MP upkeep units like efreeti and nymph (cast them first), 3) Adding ultimates to an already-large stack (cast them last).
Simple and Effective Stacks
As many griffons as possible plus a single casting of nix. Defend with EA/Satchel -- virtually unbreakable. Attack super-thin blacks with EA/RoAC for zombie devastation. Recommended as a first stack after exploring.
Tree/EE/Drake/Efreeti Pretty solid. Efreeti summon surprisingly fast. Defend with CH/Ash
Tree/Nix/Nymph Requires some calculation to balance with as many nymphs as possible. Little more than a novelty stack for hunting reds (use monkey brains).