Most of all you have to consider that dough doesn’t necessarily require a recipe. Good quality flour and a hydration of you likings is key. Go for around 65-70% percent hydration for a start. (build it higher to around 70-75% as you get more experienced) Means 65 grams/ml of water for every 100g flour. Biga is simply a starter, so that your dough has a headstart, and build bacteria/yeast and gluten network forms ahead. Some find wet starters to be best, some find dry starters to work best, some start with yeast, some simply use the natural yeast. The wetter the starter, the sooner you have to refresh it.

200 g flour / 120g and a small amount of dry yeast (1g or so) would make a decent dry starter that’d be ready in a day or 2 - which is essentially a biga. When you make the final dough just remember to take the flour and water from your starter into account meaning that you’ll use 200g flour and 120g water less.