Things I have learned the hard way about making vegetable curry:
1. Do not throw things into the pot, even if the recipe calls for them. Add spices, garlic, salt and heat (pepper) bit by bit, to taste.
2. Have a giant pile of tasting spoons handy. Taste the curry after you add each ingredient.
3. The lady on youtube who says you can just dump in mixed vegetables is LYING! Veggies cook at all different rates depending on type and how you cut them up. Knowing which veggies to put in when is an art form.
4. Eggplant can make you sad. Removing the bitterness is harder than the how-to's let on. To avoid eggplant failure, cut off the skin, then cut it into thin slices and do the salt treatment.