Users who are dilettantes, casually curious, or just in it for fun [not to imply that I disparage those types] should generally, in my opinion, start low and stick to mid range doses where they can play in the psychedelic surf and have fun without danger of drowning in the rainbow sea of mind-made realities where rapture can be so intense as to be just as dangerous as abject terror.

Users who are trying to do real, serious spiritual or psychological work on themselves or want to explore other realms in a serious manner should also start low and then progressively work up. If your goal is to use these tools seriously you should know them at every level from threshold to the highest dose your willing to go to and by initially starting low and gradually increasing you can see the progression of effects clearly without the confusion or disappointments caused by randomly switching from high to low doses.
If someones calling is to do huge doses, thats perfectly fine. But do it responsibly, without big jumps above what youve previously done. This way you learn more, see more, and dont pole vault over the maximum dose you can handle.
I'm built like an 11 year old girl, whip thin and weighing just 54 kilos, and I've repeatedly done 20 gram doses of ACRB and 750 mg of mescaline with harmine predose, but I built up to those. I couldnt have handled them otherwise.
I tend to focus on just one or two psychedelics at a time for several years straight. When my father was sick and dying and I needed to do some serious personal work to correct my path I worked with psilocybe mushrooms for two years. I gently tore them up and air dried to a 'cracker dry' state and then desiccated them for two days prior to storage. I started with repeated mild 1.5 gram doses and worked my way up to repeated very potent 7 gram doses before taking my freedom to wander around the middle of that dose range. To my continued surprise the dose that led to the most personal transformation, the dose that taught me the most, the dose that literally changed my life and single handedly justified those entire two years of work, the dose that was so complete that I saw a female forest spirit talking to me that dose was only 2.65 grams and it came after I had previously worked up to 7 grams. The only trip I reflexively think back on when I imagine the healing power of mushrooms: 2.65 grams from a ziplock bag full of shredded and mixed mushrooms which I eventually consumed all of.
Explore all you want, but never make the mistake of assuming you need high doses for profound effects.

And keep a personal psychedelics journal, preferably an encrypted one.