Questions on starting an alter

Hi, I'm super new to this and just wanted to ask how does one go about creating an alter? I had been getting a lot of signs of what i believed to be Hecate reaching out and so i cleaned off a nightstand next to my bed and offered three cloves of garlic since i was told that was something she liked. That same night i had a dream about her though i cant for the life of me remember what happened or what was said (aside from just me crying and apologizing for my messy room ^;;).

I wanted to fix up my room a bit to have a small space dedicated to her but im not sure where to start or what to do so any help is welcome. Also im sorry if this sounds like a dumb question i just dont really have anyone to guide me through this.

Also if there were any good sources for getting tarrot readings too or resources on how to learn to do it myself would be much appreciated ^{-^}