Can you play an ability that reduces gold cost of a zero cost card to get another part of the cards effects?
Reducing gold cost
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Can you play an ability that reduces gold cost of a zero cost card to get another part of the cards effects?
It depends on the card.
If the card actually has a 0 gold cost, such as Tunnel Network, then yes, you may reduce its cost to trigger other effects. On the other hand, cards without a gold cost, such as Rings and most Strategies, may not have their nonexistent gold costs reduced.