Pact objects

I need help, I'm trying to platinum the game, but there are trophies that required me to raise the ranks of the pacts, I looked for guides and they don't explain well how to get the objects of the pacts, I know where I can farm, but I wanted to ask here what it is the best build to farm items or if it is still advisable to play online. (I started the game 2 weeks ago)