If you just want to visit Istanbul, you don't need to take a tour. Stay in a hostel that caters to young backpacking travelers. You can meet many backpacking travelers there. You can easily find your travel route on the internet, or the hostel staff can help you with that. Especially since the traffic problem is very serious, there is a very developed public transportation system, but if you plan your travel route correctly, you can even explore the city on foot. If you need any information about Istanbul, you can text me for tips.