One of the most common mistakes that causes players financial trouble is not selling back items before moving on to the next land. When you dig up a cow, fence, pit, soldier, or whatever, you get back money equal to what it costs to place that object down in the first place. So in the Shimto Plains at the winter of year 3, make sure you sell all your cows and stuff. The Tree Realms goes to year 4, so sell your stuff in the winter of that year. Each "land" lasts one year longer than the previous one.

Shimto Plains:
No hidden items. Start off by chopping down trees and planting as many saplings as you can. Repeat this for a few seasons until you have enough to buy a cow. Place cows in the south of your town, as hordlings come mostly from the north. Keep making cows and saplings so that you have 10 or more cows by the end of year 3. Don't forget to pick them all back up in the winter before you go to the Tree Realms of Alburga!
Tree Realms of Alburga:

Plant as many saplings as you possibly can. Keep planting until it says "at max" in your inventory box. After the hordlings come, plant more to replace the ones they destroy. After a few rounds of this, the Dryad will give you the Boots of Boogie.

Fetid Swamps of Buuzal:
Around the third year or so, your map will become large enough to show two "arrows" made of stones (apparent on the overview map). Dig at the intersection of these two invisible lines to find the magic flute. This is probably the most useful (and annoying sounding) items in the game.

Kar-Nyar Desert:
Keep making those waterways! A tree will grow when you get water to a certain random point. The frog wants the three foods you can find scattered around the desert--the Blue Fruit, Green Meat, and Purple Seeds. Just set them down next to the tree and he'll give you his Trident.

Frozen Wastes of Vesh:
Use bombs to blow away the snow, or summon Roscoe to melt away huge strips. Be careful with Roscoe, though--he levels houses really quickly.
Horde Schedule (first 10 years)
Here are the hordes to expect each season for the first 10 years.

<------------> <-----------------> <------------>
Yr 1 Yr 2 Yr 3 Yr 1 Yr 2 Yr 3 Yr 4 Yr 1 Yr 2 Yr 3
#1 5678 6864 7345 666x 7x-8 8--- xx-- 78-5 85-- x---
#2 24 12 4 8 --36 3
#3 12 354 x 335
#4 122 3-1 6 --1- --1-
#5 ---1 --1- -1-- -1--
#6 --23 -368 -577

'x' means 10, so basically the 2nd land, year 2 is a bitch.
#1-6 are the six different hordling types. 1 is the basic type, 2 is the walking mouth, 3 is the plumber, 4 is the lumbering one, 5 is the wizard one, 6 is the crocodile one.