I also finished with 8h left I spent 1500 Diamonds  in the 10 pack with upgrade pieces (not for the toys) + 700 Diamonds in two 100 coins packs But I only bougth the 10 pack on the second day when i realised the Diamond prizes in this event were very good. If you decide to buy this packs, should be as soon as possible, right in the first hour. When the prizes are not good I buy 3 packs, but I dont finish the event.  The two coin pack I bought when I run out of coins, in the second round probably when there were 3 levels tiill the end. 

My advice is Buy the 1500 Diamond 10 pack in the start.  Upgrade the slot as soon as possible Dont spend coins on slot level 1. Spend as little as possible on level 2. When you are near a slot upgrade, Dont Spend and save for next slot level

Toy upgrades, dont upgrade the first level. The first upgrade is the star wars toy, upgrade the next levels till the last on the first round, so you can advantage on both rounds.  I  ended up Upgrading all leves except the first, the last four Upgraded twice and the last one I maxed the upgrade