You are going to get a 10001 opinions, but choose which ones to follow well.
First, you don't need much to seed, but what you seed needs to be ready to be seeded, just like earth needs tilled, fertilized, etc. Dry/dead rock that has been in water for long enough for the caked in organics to be removed and the phosphate be unbound from the rock, can quickly and efficiently take the new life from the seeded rock. This takes a long time in a vat before being put in the tank, but, as you know, this can take years in the tank.
Part of the reason that live rock is so good is because it is phosphate free and not caked with dead organics way down inside that need years to be removed.
Second, you have to know when to seed. If the rock is not ready (above) then a lot of the good stuff on the rock can die before it has a chance to seed. Higher residual N and P can kill a lot of the microfauna on the rock, but usually the bacteria, coralline, worms and some pods can live, which is still good. If you want the starfish, all pods, etc., then they tank will have to stay with a tank with parameters not-far from the ocean. ...so you might not want to seed fresh dead/dry rock right away, but knowing how long to wait can be tough to know from tank to tank.
Third, you need to understand how 1 effects 2 like I described... like actually get it. Most just ignore it or gloss over it. Think of it as putting corn on top of untilled and unprepared earth... it is going to spoil before the earth is ready. I don't mean to be condescending here, but most just do not get this and it is too important since you asked and obviously care.
Fourth, don't listen to anybody who tells you that bleach, vinegar or some acid is all that you need. ...just not true. All of these can help with some acute things on the surface but still do not all of the things in number one. You still need more than this.
If you need to do a bunch of dry rock for budget build, then get it in heated saltwater for a few months, at least. Get something in there to introduce bacteria and test the phosphate after a week. It will be high and might continue to climb in the months to come as the bacteria starts to break down some of those caked in organics which not only breaks down into residual N and P, but they also uncovered some more aragonite structure that will unbind even more phosphate. You need to treat a few times a week with some Lanthanum Chloride (cheaper and easier than GFO) with a skimmer or filter sock on the tank (or both)... and keep doing this until the P is like 1 PPB after a week or two of sitting. When the P stays low for a few weeks, then the rock is done unbinding and getting the decay out. This can take months and months, if not longer - all rock is different and there is no way to tell but you basically have to start bacteria to eat that caked in crap and also give time for the P to unbind.
Of course, you know what happens if you skip some of this... a year or two of the uglies.
In the end, just figure out the cost, effort, etc. and see what you want.
You should be able to get cultured pacific rock to go along with some Atlantic rock if you want even more diversity.
Lastly, don't underestimate used real live rock. Even though it can be full of nasty algae, phosphate, etc., you can get it back to life fairly quickly and faster than getting all of the caked organics out of dry/dead rock. There are a million threads on how to "cook" rock out there, or we can help... but it was really common and very effective before the dry/dead rock craze. I still will take/get all of the real live rock that I can, even if it was in a neglected tank... I have a rubber made 150 just for this. If you are in a larger market, be on the lookout for tank breakdowns and stuff... we are seeing more-than-normal tank breakdowns locally. When this is done, it won't be full of pods, worms, starfish and the like, but it will have bacteria be phosphate free and ready to accept life from the seed rock. If you can, start plenty early and try and do this, IMO.
