I am really confused. Which is the best option steam turbine or gas turbine for power generation in terms of cost and performance?

i think you better read "power plant book" i try to make it simple, steam turbine in big scale is more cost efficient than gas turbine, but if it is only fow low scale purpose and no steam is needed for other areas, then gas turbine is the option. sometimes in big power station. Combined cycle is used (gas and steam turbine) to increase overall efficiency to abour 54 to 60%, while steam turbine alone and its generating steam overall eff is around 35%, and also gas turbine.