I'm one of the oddballs: I manually fight every encounter in the Spire. I do this because I really like manual battles, but they're so freaking slow that tourneys have become 99% autofight. Plus, tourneys are the same enemies every time, so it becomes boring. Spire fights are more interesting and provide a challenge I enjoy. Note: when the Spire came out as single player, I spent 2-3 months pretending it was a second game I played and I 'budgeted' $20/mo for diamond usage for that 'game'. I don't think I came close to using up my budget, lol. Maybe that first month. I used diamonds to restore troops while I learned. Now it's very rare for me to need to do that at all. I have run into a 3 wave boss fight at the end of the first floor once since it became multi-player that I just could not win (or it would have required hundreds of diamonds to do so) and I used the diplomacy option then.
In my elementals city I go to the first gate in the Laboratory(last chance at a teleport spell); in my elvenars city I complete the Spire each week now (did the same as my elementals city until a few weeks ago). To keep the number of troops I need to do that, I've driven my training size up (leveling Shrooms, built a few lower lvl (lvl 15 for me) armories(the increase to Shrooms training size boost from the extra armory levels is a big bump) and I feed the Brown Bear once/week and push through troops. I also try to leverage expiring military boost bldgs and feeding the fire phoenix. Ex: I can do my first tourney round with only a fed phoenix and hold off setting those bldgs out until Wed. Then, they don't expire until after the Spire launches on Sundays. With the Spire being a net gain in time boosts, I can run through the first floor on Sunday, knowing I'll get those time boosts back.