Personally,
I devoted 9 expansions (3x3) to Dwarves and Faeries. Probably going to have to expand that for Orcs. Currently, I am planning on 12 expansions (3x4) for Orcs.
Haven't been tech-locked yet
Tolerance for tech-locked: 1. With the percentage-based mechanics for AW's these days, KPs are most effective in the tech tree if at all possible. Otherwise, if you are in a good FS, then a hyper-visit thread can be a KP sink. But I only sink KP into AWs if I am tech-locked, because progression is key.
How well did I plan: 9. I not only used the Architect, but also consulted with people on this forum about what my anticipated needs are and expected space requirements.
When starting a guest race, consider the size and shape of every other building that will upgrade during that act. For example, when I first got into Dwarves, I had to shuffle some things around because my residences were changing shape, and my tier 1 boosted was not only changing size, it was changing the direction that it was aimed, meaning I had to shuffle things around significantly. Because I had already set aside a significant space for the Dwarven buildings, I had room to shuffle things through, it would have been MUCH harder to do that if I had already filled in that space with Dwarven buildings. So do yourself a favor, and shuffle around space to accommodate not just your guest race buildings, but every other building that will be upgrading as well. Because I guarantee you're going to have some buildings which are going to change significantly in geometry, and shuffling around to accommodate that before it unlocks and you have empty space where your guest race buildings will go is going to be significantly easier than if you do it at the last minute.