Gideon perfectly represented Israel's judges: He was a humble farmer who was plucked from obscurity by God to become a mighty warrior and lead the Israelites into battle to deliver them from the crushing oppression of the Midianites. At first, Gideon questioned God's messenger to understand why his people were suffering if God truly loved them. "Didn't the Lord being us out of Egypt? But now the Lord has abandoned us and given us into the hand of Midian!" When the Lord answered "Go in the strength you have and save Israel out of Midian's hand", Gideon responded by asking for "signs" for God to prove Himself.
The "heroes" of the Old Testament weren't perfect people who never made mistakes. They weren't super-humans who never questioned God or lost faith, and they weren't mythical beings who were invented by ancient writers to fool people into following false gods. The leaders of the Old Testament were real flesh-and-blood humans with all of the flaws, doubts, and weaknesses that we share today. But God raised them up anyway...*flaws included*...to fulfill His divine will, deliver the Israelites from hardships, and prepare the way for the coming Messiah.
Gideon eventually believed in God because he approached God with a humble and open heart seeking answers to life's toughest questions. Gideon respectfully asked God to convince him that He was real, and God patiently worked in Gideon's life until Gideon developed a strong and enduring faith.
It's not a sin to ask God for help believing in Him! In fact, God already knows we'll all struggle with faith at some point in our lives and He *tells* us to humbly ask Him for more faith! And God is supremely patient with us, sometimes watching us take two steps forward and one step back. If you've been struggling with faith, it's time to take the next step and ask God directly for help believing...He WILL help you!