OK, you get the most well-known Fourth Division character, Hanataro Yamada, in chapter 92 (volume 11), and he's running around with the main characters through at least volume 14. The 3rd Seat of 4th is in the omake pages after each chapter in 11 and, I think 12 (my copies of 12 and 13 have gone walkabout), writing reports or, as he puts it, expressing the anguish of middle management through reports. XD But Hanataro's our biggest source of info on them.

The manga are about 8 bucks US each and I would never ever suggest you download the scanlations from stoptazmo.com just to see if you liked them or not. You kinda need to read the first story arc, mostly a set of not-very-connected stories set in our world, to be introduced to the characters and get the background you need before heading into the Soul Society arc, where we meet all the wacky shinigami/Soul reaper characters.