For growing mango from seed, or really anything from seed, you cannot beat a small plastic container (like what cottage cheese, sour cream, or green yogurt might come in) filled halfway with coconut coir. It's absolutely the best medium for germinating seed. Fill halfway with coir and water once a week. Coconut coir keeps water evenly distributed and I've never had a seed or seedling mold over using it.
I personally use 2 lb greek yogurt (or soup, as in from Costco) containers because the extra height also lets me keep the seed in there longer and develop initial root structure. That's incredibly helpful for transferring to pots, and a little coconut coir in the soul doesn't hurt.
I personally use 2 lb greek yogurt (or soup, as in from Costco) containers because the extra height also lets me keep the seed in there longer and develop initial root structure. That's incredibly helpful for transferring to pots, and a little coconut coir in the soul doesn't hurt.