For those who want to grind this out the normal way, play normally until you have enough money/gold to purchase the llama horn and all of its upgrades to maximize the number of llamas spawned when picked up. After you are used to playing and learn how to best maneuver the wingsuit, you can easily find 3+ llama horns (green pickup) before you reach 10,000m in a run, netting around 100 llamas if all were tagged. Since the achievement is for 100,000 llamas, this will take less than 1,000 good runs (10,000m per run). Don't forget that you can do a loop with the wingsuit to better position yourself for pickups or llama herds. Good luck!