tactics gives a better coupon value per credit. However, it is diversified which makes some of the value became sunk cost and useless. That said, as you will also get random pages elsewhere, statically speaking the sunken stuff can still be useful if you end up getting some of those pages multiple times and get lucky on upgrade.

Advanced thread is safe, but it really cost a lot to get anywhere.

Personally, I would suggest you get tactic pack until you have at least one lv 5 tactic. At which point, most of the pages you get will most likely be never useful. Then get advanced threads.