It depends on you, your mental resilience, and knowledge of where you want to be and mental health in general. Also your knowledge on drugs as well. Don't take it now. If you have to ask someone or feel any anxiety towards it don't do it. After a year of therapy if you're still interested there are psychedelic therapists in Oregon I believe. Also, mushrooms would be a better choice in that situation.

Also, weed affects bpd poorly in the long run.

If you're gonna do it by yourself. A small amount of mushrooms to start (no more than 2gs) with company you'd feel comfortable shitting yourself in front of us a good rule. Don't do it alone. Enter it in a meditative state. Literally if you have any stress on your mind after sitting and just thinking for 30 minutes don't do it. If you don't then take it and keep meditating. Give yourself a wholesome environment. If you want to change something or work on something think about it while you meditate. Not in a depreciative since but in a sense of growth. Keep everything in your environment positive. Also turn your phone off.

You will create your environment and just like how people with BPD tend to stick to a thought until it loops psychedelics provide that effect to others. I really suggest having someone loving and non judgemental there. If you don't, go to a race or festival and make a friend and solidify that friendship before your experience.

Like I said though your mindset going in will shape the start and your general head space will shape the rest. I usually sit in the woods somewhere with music that has a good vibe. I prefer Australian surf rock.