I use autofight, and I only fight the battles that are one round or occasionally 2-round ones if the enemy troops are favorable (in general where they are all weak against one type of unit and that unit is either light or heavy ranged or possibly heavy melee, as I play elf and my mages are worthless).
I convince the rest of the time and have used the strategies presented in the videos. Once I get to the encounters where there are 5 or more options, if I don't get at least 2 "no one needs it" on the first offer I withdraw and start over. I use less goods overall by withdrawing than continuing in those circumstances.
I also have built my city in a way that creates the lowest possible Tournament and Spire costs. My city is substantially smaller than average (31 total expansions in Dwarves, will grow to 36 expansions as I enter Fairies around the time of the next event). I keep the size down by sacrificing armories and workshops and compensate by collecting from workshops and barracks frequently during the day. I also rely increasingly on Magic Residences and Magic Workshops as I win them in the Spire. I currently only have one AW, a Golden Abyss, although I plan to add the Martial Monastery when I expand my city for Fairies. The main factor increasing my costs is that I have maxed all my relics boosts, but this pays for itself. A combination of Spire wins, crafting, and Events gives me abundant coin rains and supply instants if I'm falling short on coins or supplies.
I recognize that when I begin using orcs and mana for convincing in the Spire this will change the dynamics somewhat. I plan to rely heavily on event buildings for mana and orc nests for orcs. This will be practical because my slow pace of progress through the game both allows accumulation of event buildings and materials to upgrade them (blueprints and RRs).