Exactly what @FraVit93 said
Usually something like 3300 tp team is sufficient to get you through the seasonal event if you have items. Last stage might require you to buy a continue with gems but that’s a cheap price for a tabard.
Where tornadoes, time stops and potions fails (their help is proportional to your heroes) you can go with damaging items as arrows, axes, bombs and dragon attacks
Carpet bombing is your friend. You’ll usually find one lvl along the way and the final lvl to appear as showstoppers. Approach those with 5 arrows, axes, bombs and dragonattacks, and mop up what remains. Okay it’s a bit expensive in terms of consumables. But you can save up for these rewards, and there’s something intensely gratifying about carpet bombing.
I barely managed to get the first ascension item during the sand event (the orb); I couldn’t even try for the darts. My main goal since then has been to get my team and forges up high enough so I can beat the next seasonal event. The difficulty of the events gave me a goal without being totally unreasonable and I’d be rather disappointed if it changed before i got a chance to see if I’ve completed my mission.
With right 4* heroes those stages should be doable. I have over 4000 teampower team and I love those event just, because at least there are some challenge. If all stages were just as easy than regular ones, this game would be very boring.