I've made a few sourdough starters over the years and have met with descent success, but I just don't bake enough to keep a starter going, so generally, I build one for a recipe, bake it, and then discard it. I've got some family coming into town in a few weeks and they've requested that I bake up some bread, so I figured it'd be a good time to get a new starter going. That being said, I haven't decided on a final recipe yet. How important is it for the starter recipe to be similar to the final dough recipe? In other words, I probably wouldn't want to try to make a rye sourdough with a wheat starter or vice versa. But what about if it will be a wheat dough, mixture of white flour and whole wheat? Do the ratios really need to be the same? I can build this however I want (obviously) but wasn't sure if I need to commit to a recipe this early.
When you decide what you wish to bake just begin feeding it the correct flour and to the correct hydration. But when making one it's not important.
Many people keep one ongoing starter and make many different types of bread by taking a little off and building an off shoot starter to the correct requirements - aka a levain.
Your starter can be made from any flour or combination of flours.
I have two starters: One is an all bread flour starter which I use for whole wheat, and bread flour recipes.
And one is a 100% rye starter I use for rye breads.
If, after your baking session you decide to carry on baking, you can keep your starter going, and change is it as you please. I've changed my bread flour starter to a wheat starter, and back again as the mood has taken me!
If you decide you might want to bake again soon, your starter can be refrigerated, and fed occasionally, or it can be frozen or dried.
Ratios for building a starter are generally 1:1 flour to water
Once your starter is active, you can continue with 1:1:1 starter:flour:water
If you find yourself wanting to bake more, and frequently enough that you need more starter, you can increase to 1:2:2 starter:flour:water
In any case, for a good, robust starter you should allow 7-10 days for the starter to be strong enough.
Good luck, and happy baking!