I live in Southern California and have a yard and garden that provides me with wonderful flower blooms.
I use my roses, gardenias, and my flowering trees - lemon blossoms, orange blossoms, and grapefruit blossoms.
This is the process for the flowers. Bring them into the house, separate all of the leaves, twigs, green parts, and petals that are bruised and damaged and discard everything that is not a terrific looking flower. Now
lay the flowers on paper towels to absorb the moisture. Let them air dry for a while until they feel dry. If you tincture wet materials they turn black, mold, or it just doesn't work.
Fill a clean glass jar with high proof alcohol and put the blooms in and make sure all of the blooms are covered.
Replace the blooms with new ones as often as you can. Repeat until you are satisfied with your results or until your garden stops producing. You can shake the tinctures and check on the smell daily.
I have also put gardenias in jojoba oil and once again it is the same process. This method can cause the blossoms to mold. Be careful of this. If it starts to smell off throw it out. You can remove the petals after one day or leave for several. This is your call. It takes many changes of petals to build up the strength of the gardenia smell.
I also tincture other items like vanilla beans and use those tinctures in my perfumes and custom couture perfumes. Some of my flower tinctures are only used in my one of a kind bespoke perfumes.