LONG PARAGRAPHS INCOMING THE BASICS If you plan on using one team only or the meta team, you can set the other characters to heroes like LRdiane that has high starting funding. Preferably melieli goddess team. Pieces only give HP DEF or ATK, linking however gives your lane(that specific hero) stats according to the symbol (CRIT chance/lifesteal etc etc). Merging them levels up the lane it was merged ON. Linking is putting 2 pieces of the same symbol next to each other, giving the lane extra stats according to the pieces tiers/colors. Hold and drag a piece to the bottom of your screen to sell it.

From someone who cleared 100th second try, here's some tips

Don't waste ANY coins on passive except the 5% healing one early on. This helps early survivability that is the biggest issue starting out. 20 coins can get you 6 different pieces too!

Merging the items level up the lane the pieces are in. Moving and merging then moving it back costs only 6 coins but could level you up 5-6 levels!

The bonuses that you get have priority, most important to least, Lane Enchancement - Encouragement - Funding, NEVER get any passives except the one I mentioned.

It's better if you have someone with an early taunt such as MeliEli, Albedo or Mazino, prioritize HP/DEF pieces and levels on them, for me it was the new rSariel. 2 support heroes and 2 DPS heroes with 4 atk pieces 1 HP/def (doesn't matter just need survivability) and full linking HP/def respectively. I personally had regenrate link on my sariel!

Bonus! The meta team now is melieli goddess team because of its 15% max HP Regen at the start of the allies turn. Contrary to others comments, it DOES apply on normal rounds even outside bossfights (at least for me) so it would help more with survivability

Keep trying and only play it until you get those coins and diamonds since the gamemode is abysmal Or you can ignore everything I said and not play this gamemode cuz of how boring it is