Nope, you can farm harrow in less than a day, and get all the resources in that time lapse, and you wont spend a dime in it! Garuda needs tier 4 gems, if youre mr 20, you got 21k standing points daily, you will need to spend 4 days or so to get on tier 4 in fortuna. So no, garuda is not easy to farm.
But I dont need to be in the last standing level to do a Zaw. In fact, im on the third level and I got my Zaw, in fortuna you need to be on the penultimate level to do a kitgun, or a moa, or gara. The problem with fortuna is that is not congruent with its standing levels, I can buy all the bp of a kitgun but I cant make that kitgun, in cetus that doesnt happen.