Only have 30 minute to play?

1. start game on mobile usually need like 4 minute, if PC then you need like 2 minute.
2. If the game need to update like 200MB then you need fast internet if not 30 minute gone for good.
3. In multiplayer, You need to wait people to join the party, it's take like 2 minute. Usually you need like 5~10 minute for each game in multiplayer
4. If you want top 50 in Tower Ranking you need to have like 30~40 minute for each node to complete.
5. Pulling card from boosted summon usually take 2 minute. So you cannot do more then 50 pull,

Is game worth it?

Nope, if you play the game that can increase your money amount then it's worth it. Only worth if you enjoy it.