In honour of the centenary, I have decided to create this thread. IOTL, Gallipoli was an absolute disaster. ANZAC Cove was an awful place to land, likewise with Cape Helles.
A successful strategy would be too land troops first instead of trying to sail up the Dardanelles. It would be hard, but better landing places would help.
If they do take the peninsula and minesweep the Dardanelles, then the road to Constantinople would be open. The Russian Navy can access the Med, but I'm not sure what the effects of that will be. Eventually, Constantinople will be taken and the Ottoman Empire will surrender.
The Bulgarians will likely join the Allies and the Austro-Hungarian attack on Serbia won't happen. The Serbians, Greeks, Bulgars, British and Commonwealth troops could attack Austria-Hungary to help out the Italians. They could also help start multiple rebellions that will doom the Empire by the end of 1916 at the latest.
By 1917, the Germans have lost both their allies and are in dire straits. After the fall of Austria-Hungary, the Russians will join up with the rest of the Allies and invade Germany from the east. This could lead to riots and the end of WW1 in 1917.
What happens next?