Don't let this issue keep you from church. As a new Christian, you need the fellowship of other believers, and you need the spiritual strength you'll get from hearing God's Word taught and preached each week. Jesus promised, "Where two or three come together in my name, there am I with them" (Matthew 18:20).
And no - the Bible doesn't tell us how to dress when we go to church. Traditionally, people often have dressed up for church out of respect for God (which isn't wrong). But God is more concerned about our hearts than our appearance, and church shouldn't be a place to show off our new clothes or compete with others by what we wear. The Bible reminds us that "The Lord does not look at the things man looks at. Man looks at the outward appearance, but the Lord looks at the heart" (1 Samuel 16:7).
Ask God to lead you to a church where you will feel at home - and where you will grow stronger in your faith. Don't limit yourself to the main weekly service; seek out other opportunities for fellowship and growth (such as a Bible study). Let your pastor know, too, about your recent decision for Christ, so he can help you and encourage you.
In addition, learn to walk with Christ every day. Set aside time to read the Bible and pray. Commit every decision to Him. And pray especially for those around you who don't know Christ, asking God to help you be a witness to them. May God bless you.