i've set up a diy co2 thing to one of my tanks and currently am stuck on reagents for it.
i bought a bred yeast which comes in blocks but not sure its the right way to go.
alternatively i can buy wine yeast, champagne yeast and beer yeast from local brewery. they are kinda pricey tho (5g/2eur).
so the question is what kind of yeast i want to run nice and long?
I use the cheapest baker's yeast that I can find at the grocery store. It is usually sold as "active dry".
You can also experiment with different types of yeast (as you mentioned, wine, champagne, etc). These will probably work, and may provide CO2 for a bit longer, as the yeast can tolerate ethanol buildup to some degree before they die off (compared to regular yeast). However, the cost may be a prohibiting factor.
Champagne yeast works very well for DIY co2. I used it with mine and noticed much longer production times.
If you want to reduce cost simply put a little bit of the yeast in a separate bottle of sugar water and allow it to start to multiply. Be sure you don't have a cap on the bottle or it will explode haha. When you feel like the yeast has multiplied enough put it in the fridge and you can use it the next time you replace the solution in your DIY co2 setup. Save some of the sludge at the bottom and refill with more sugar water. You will never need to buy yeast again.