Hi there,
You ask an interesting question there. As somewhat of a terrain freak I have spent quite some time in my gaming table.Nothing beats playing a game of warmaster with well painted minis on an interesting and well finished table. Here is what I would do in retrospect:
Hills are the first think to put on the table imho. Otherwise you get the feeling you're playing pool.
After that I would certainly foresee some villages as they create perfect objectives and give you a reason to really advance those infantry units. Combine them with some small walls and hedges that can also be placed anywhere else on the table.
Fields are very easy to make and give a clear advantage to infantry, a good choice when you don't have a lot of terrain yet. They fit in nicely with the villages. Also they provide slightly different rules as they are passable by cavalry as opposed to the villages.
Next would be woods. They block line of sight for everyone yet are passable for infantry. They have more or less the same gaming effect as villages but you can put more of them on the table without getting the feeling you're playing Mordheim.
I have recently made some larger woods (40+ cm diameter) and use them in combination with roads that wind through them. Cavalry can go over the road but you never know what might be lurking in those forests

. This combination is quite interesting as well. So the roads would come right after the woods.
My next choice would be river or cliffs whatever you prefer most. Maybe best to take cliffs first, they add more 3d to the battlefield. I also have some cliffs that can be combined with more gentle slopes. About 10cm high is enough - you don't need higher as it will only increase the storage space requirements. The combination is quite interesting:
- You can use the cliffs as a narrow gap to be defended/broken through.
- You can create impassible obstacles in the middle of the table with these cliffs.
- By combining cliffs on one side and a gentle slope on the other you can create interesting objectives as well. Ideal if you also put a village on top.
- You can also use the cliffs over the length of the table with slopes in the deployment zone. This creates two different battlefields so you have to think wisely during deployment which troops to take the high side and which the low side.
A river is interesting for some battles but creates a clear attacker and defender, unless if you use it to split the battlefield in two parts using the river. When made properly it is a real eye-catcher though. For me rivers are more to look at than to play with.
Swamps and lakes are identical when it comes to gaming effect. They allow interesting spots for artillery but block to the table for most troops. Having one is more than sufficient imho. So don't overdo those.
Then there are some more exotic pieces of terrain such as stone circles etc. They mainly provide objectives and the occasional special effect (like spell casters having higher chance of success when they are within the terrain piece). They basically add flavor but you don't want to put it on the table each and every time as they quickly become boring.
I'm thinking about creating some brooks next. They will be impassible for chariots and provide defended status to infantry. So they provide a less obtrusive version of rivers. Crevasses would also be fine if you would be fielding a chaos or undead army.
That would be my preferred sequence, not only for playability but also when it comes to complexity and time to make them. 10mm houses can be bought, painted and deployed. Hedges too. Big forests can also be made quite fast (I recently posted a link somewhere). Cliffs require more time and certainly rivers if you don't want to put them on top of the table.
There was this great article about building warmaster terrain by Stephan Hess quite a while ago. I don't know if I have an electronic version, maybe someone else here does?
Good luck,
Jo