How important is CO2 at seedling stage?

No point in investing in Co2 for your current setup. You will just waist your money and inject harmful Co2 into the air for no gain. Your 200w lights are not big enough to gain anything from Co2. And unless you have done your research and have been growing for awhile I would not try it. Your room needs to be basically sealed like a vacuum chamber to even start, then it’s a dangerous and tricky balance trying to balance everything in a perfectly sealed room, especially heat. Next is the fact your lights are nowhere near what you need to get anything extra. You need BIG lights for Co2. The Co2 basically allows your plant to transform the extra light through photosynthesis to energy for your buds. But if your light can only give out basically what your plant can handle already with out any Co2 added, the extra Co2 does nothing and literally blows away. Basically your plant doesn’t need it for photosynthesis because it already has enough naturally for the light you have. I ran a Co2 grow bag once under one of my 1000w lights but it was just to hard to seal the tent to keep in the Co2 and my exhaust just sucked it out. If I turned off the exhaust or scrubbed it back in the tent my temps skyrocketed! Very hard to do successfully, waste of money if your not 100% invested and have the proper grow room and equipment. Cheers💨