Can I be just a Christian? Yes, of course. Anyone who obeys the gospel; that is, anyone who believes, repents, confesses Christ and is baptized for the remission of sins becomes a Christian.
Can I be just a Christian and follow the Bible alone as the only rule of faith and practice – not adhering to any man-made creed? Yes, of course. The Bible is the inspired word of God and provides Christians with all the instructions they need. The Bible says, “All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: that the man of God may be perfect, thoroughly furnished unto all good works.” (2 Timothy 3:16-17) Men have taken it upon themselves to write out official statements for the faith and practice of Christians. But whether it is called a creed, catechism, discipline, manual, book of order, etc. all such are the invention of men and have no divine sanction.
Are there any people today who are just Christians, who have no creed book but let the Bible itself be their only rule of faith and practice? Yes, of course. There are thousands of just Christians throughout the world. The North Main Street Church of Christ is such a group of people.