With breeding without the charm it's like 1out of ~4500 or something chance of getting a shiny. (the last gens it was 1 out of ~8500 chance.) My brother got a shiny espurr by fluke that way with a perfect nature, but horrible IV spread. But In the game code and early days of XY people found out that each egg had a code that matches with trainer ids. So if the egg's hidden ID was 12345 and my trainer ID was 12345, that egg is a 100% a shiny if I hatched it. If i gave it to someone else with another ID, it just a normal, non-shiny pokemon. Nintendo patched the exploit and blocked the program used to find out the hidden IDs
But if you're ever gonna go the egg route it's gonna be long explaining, i recommend:
-getting a 'totally legit' 5-6 IV Ditto, and giving it destiny knot
-the pokemon (lets say he has 0IVs) you wanna breed with the right nature. Give that guy a Everstone. Everstones pass on the holder's nature 100%.
With each egg being hatched, it takes the IVs from the ditto to the pokemon, and eventually you'll get a 2IV or 3IV pokemon. Take this pokemon and replace the parent at the daycare. Give them the Everstone again and hatch more eggs.
3rd generation should now have 2-3 IVs 'permanently' as 90% of the eggs will have 2-3 random max IVs. The ditto will now put in the missing 3 max IVs. It's gonna get tedious but you can stop at either 5IVs with the missing IVs being in a shitty stat (ex: Talonflame having 31/0/31/31/31/31, that 0 being Attack.) or go full tryhard and get a 6IV pokemon. To get that put up the 5IV baby with the ditto and have a ton of patience.