Yes, it is hard to know what is going on without more information.
I'm assuming the 100% means you have 100% efficiency (i.e. your turbine has enough blades to support the steam you are giving it).
Did you add coolant ports to your reactor or are you using a different steam source for your turbine?
How are you getting steam into your turbine? Are the reactor and turbine right next to each other with coolant ports touching, or are you using some kind of fluid transport between them? Most fluid transport pipes/ducts/conduits have limited throughput which can limit how much steam gets to your turbine. Check your reactor. If the steam buffer is full and the reactor is running extremely hot, then you're not getting steam out of the reactor quickly enough.
I will assume that your reactor produces at least 2000 steam per tick. Each blade allows your turbine to consume 25 steam per tick without loss, so you need 80 blades to use the maximum 2000 steam per tick without efficiency loss. You then want coil blocks, however many it takes to run at around 1800 RPM (I prefer to put the minimum for it to run at less than 1800 RPM, then use ComputerCraft to toggle induction so it runs at 1800 RPM). For ludicrite (the best material), you need 32 blocks. Next best is enderium, which I believe needs 37 blocks.
The size of reactor that you need depends on how much power you need and whether you want the power while it's still passively cooled or if you can do with less power until you reach the point of making turbines. I have a 13x13x6 (interior) with 21 control rods. It was enough to run a Speed III ender quarry while passively cooled, and produces about 48000 mb/tick steam when actively cooled and with control rods out. Note that I had the reactor planned before the ender quarry's power drain with Speed III was reduced - the original plan was to use Speed II while passively cooled and upgrade to Speed III once I had around a dozen turbines. There is no point in making an even bigger reactor since actively cooled reactors cap out at 50000 mb/tick. Sure, you can make an enormous passively cooled reactor but it's going to be inefficient.
Of course, you don't really need a very large reactor unless you're building it for the heck of it and have the resources (I had a bunch of resources from the Ender Quarry running without Speed before making the reactor) or if you have a mod which eats up a crapton of RF.
For example, a Speed III Ender Quarry eats up about 20k to 30k RF per tick. There are few things that use more than this. Adding Fortune to your Ender Quarry will raise the power drain way up but is considered not to be worth it. Building a whole bunch of ender quarries with Speed III will also gobble up power. Another thing that could eat a lot of power is RFTools dimensions. Something simple doesn't use a lot, but if you want a world made from diamond blocks or something, expect to require north of 100k RF per tick.