I suggest a half-eight of mushrooms. Many have said, and I agree that mushrooms are one of the more psychologically challenging psyches, BUT if we're talking about the most common commercial P. Cubes (gold caps), then the dose-response is fairly consistent. You almost can't go wrong with a half-eight, regardless of the batch.
On the other hand, LSD is hard to dose properly because of inconsistent potency, and research chems are hard to dose because a few milligrams over-dosed can be way more than you want to feel.
I also highly recommend keeping a benzo or antipsychotic on hand. This way, if it goes wrong, you can abort the trip by popping a pill.