im looking for any drama where male lead was poor but turn powerful or rich.

for example like in kdrama giant 

Cunning Single Lady

Not sure if you are only looking for epic, long dramas like Giant, but here are some with MLs who rise up

• Baker King Kim Tak Goo
• Itaewon Class
• Money Flower
• Doctor Prisoner

The Dark Lord

Behind Your Smile, but he is toxic and manipulative

• Mr. Sunshine - His power is tenuous.
• The Legends - His father was powerful but abandoned him.
• The Tale of Nokdu - He grew up poor because his adoptive father saved his life and was always on the run / in hiding from his powerful birth family.