My first buy ever was G1 2001 Gali and Lewa Mata, The first one that I opened and built was Gali.
My most recent buy was Master Tahu, Protector of Fire, and LOSS, built in that order.
Fun fact, I have a little bit of OCD, and after buying all the Toa Mata in the order of Gali, Lewa, Kopaka, Tahu, Pohatu, and Onua, I then proceeded to buy as many of the sets in that order as possible: Blue, Green, White, Red, Brown, Black. Even with the waves where I didn't buy all six, I usually bought them in that order. meaning that I have a lot more blue and green pieces that other colors. The last complete wave I bought was the Phantoka (Toa/Makuta, not Matoran/Titans/Mistika), and I'm pretty sure that they were in the pre-established order. You will be happy to know that I have broken that trend for G2 Bionicle, having bought Lewa, Pohatu, and Tahu in that order.