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Grafting is not easy in the beginning, do yourself a favor and plant every single mango seed you come across this summer. Read up on the proper soil for mangos, healthy seedlings give you a much better chance at success. Read even more about the proper grafting tools, watch a bunch of videos on the various techniques. Treat grafting like surgery, everything must be clean, you want the sharpest tools and you need to make clean, even cuts. Your first attempts will likely fail, my first season I had a < 10% success rate (ran out of seedlings quick, too). I'm running around 80% now, proper tools and techniques make all the difference.
If you just want one tree, plant that seedling you have in the spot you want the tree to be. Give it a full season of growth in-ground, and graft to it next season. Healthy in-ground trees are the easiest to graft onto, they make the best patients