If you want to join a gallipoli battlefield tour, you should go to Çanakkale at first. There are lots of companies which organize gallipoli tours in Çanakkale and Eceabat. Generally the tour companies organize their tours with minibuses. A seat per person in a minibüs is about 45 Turkish Liras. But some companies organize private gallipoli tours for one to three people. Those private tours cost about 220 to 250 Turkish Liras.
When you decide to visit the battlefields of Gallipoli, you will have lots of tour options from budget to top class, short time to overnight tours. If you choose day excursion gallipoli tours it is the shortest and the cheapest tour. You met with your tour guide in late morning in Eceabat. You visit the all major historical locations and in the evening your tour finishes. There are also overnight gallipoli tours from both Istanbul and Çanakkale. Via 2 days tour you will be less rushed and you will have chance to visit Troy also. You will stay near Gallipoli in a comfortable 3 star hotel. If you choose to join private gallipoli tours it will cost more money for you and your group but it will be a more specific and comfortable tour for you. You and your group are taken by a Professional driver. And if you want them to take you from Istanbul, they accept your wish and come to take you from Istanbul. Of course it will cost you extra money. They carry you with comfortable air contioned minibuses. Because of having plenty of time, you can see wherever you want.
If you have more time to travel, you can join four days gallipoli tours including Gallipoli and Aegean shores of Turkey. During those tours you will see Gallipoli battlefields, Troy, Ephesus, Pergamum and Pamukkale. Each year on April 25th is the Anzac Day in Gallipoli. A dawn commemoration ceremony is held every year on Anzac Day in Gallipoli. Most tour companies organize some special gallipoli tours on Anzac Day. You can join those tours to see the dawn ceremonies for the commemoration of Anzac soldiers.
If you choose to visit all the battlefield of Gallipoli by yourself and by your own car, you can rent a car in Çanakkale. Maybe it can be more tiring but it will be more enjoyable for you. It is up to you, choose one of the options.