Finding Truth when you seek it working with Santa Muerte is extremely liberating albeit extremely painful to hear. It opens up avenues to you when you open up you heart and make yourself receptive to her wisdom and words and give yourself over completely to hear what it is she is saying to you.
When I work with Santa Muerte it is always a journey and an experience. I start by setting my intention and giving my altar a cleanse. Having a specific altar to Santa Muerte separate from all my other altars. Keeping a separate temple to the Demons, a room specifically for Demonic workings. I have a room set up specifically for the Dark Goddesses and I have a room in my home that I do all other things.
When I started working with Santa Muerte, I took a room in my home that is not used, and took a private corner and set up my altar. I have a wooden table, with pure cotton cloth and a Santa Muerte Statue on it, It is the 7 colored statue. If you are looking for a good Santa Muerte Statue, I suggest going on Etsy and looking at this shop https://www.etsy.com/shop/DKRZDesigns or this shop, https://www.etsy.com/shop/CreepyOdditiesShop, I have purchased statues from both, and they are equally amazing.
I do work with different statued gowns for specific needs and I strongly recommend before working with her, you learn the colors that represent what each color of the statue brings to you in your petition. I found an amazing book once and I highly recommend it for beginners, you can get it on Amazon, https://www.amazon.com/Secrets-Santa-Muerte-Prayers-Rituals, by Cressida Stone. It was extremely informative for beginners.
Santa Muerte is forgiving, and it is your intention behind your petition and if you petition a Gold Statue for protection, it is not the right one, but she will be understanding and if you explain why you are doing it, she will accept your reasons and not take exception to the mistake.
My altar has a ceramic owl on it, one of her animals of wisdom. I keep black candles and a white candle for her purity and strength. You can change and add colors according to your petition. I personally do not add any Catholic Saint candles, it is not my thing. Those are the only other additions of spiritual systems she allows, do not add other demons, or goddesses to her altar, it is considered a slight. If you really must, always put her above them. Her altar must be in a quiet, private place, away from traffic.
I am contemplating an outdoor altar as well, and will be scouting one out on my mountain home. I always keep a bottle of Espolon Tequiila on my altar and pour her a generous shot and I leave her a piece of Mexican Calcitrite stone pure and whole and really beautiful. Using Black Copal incense in her honor and have a black altar cloth at the moment, but I do change it up when I am needing different workings. People have been known to place aloe leaves, eggs, apples, dolls, many many things on Santa Muerte in thanks. What you leave depends on your work you are doing. I believe as long as it is genuine, and from the heart, it is pure in intention, then leave it.
Most importantly, come to Santa Muerte with clear, good intentions, be concise, and be open, she is non judgemental and she truly listens. She is kind, and loving and accepts all walks of life. She does absolutely not suffer fools though. If you are going to ask for her advice, I suggest you follow it, and if you struggle to follow it, go back and get help. You can find me on etsy as well as here, I am starting a new Santa Muerte line on Etsy with Rituals, Protections, Cleanse Kits, and I have recently after working with her published her Guided Meditation of Holy Death and Rebirth with Santa Muerte as a set and individually. https://www.etsy.com/shop/SatansEyeOfTheStorm
Blessings and Darkness on this wonderful journey with a beautiful Mother and finding your truth with Santa Muerte.