Xibei San Ma
Because of its location, Turkey has many advantages. With Istanbul as a starting point, it can exert its military might on Eastern Europe is militarily superior to its two immediate European neighbors, Greece and Bulgaria. It also has a pathway to the Middle East via Syria and Iraq, and a large resultant income of oil. It has fairly good research teams overall, and an IC which is substantially higher than any of its immediate neighbors. It also benefits from good relations with the Soviet Union and adequately good relations with Germany. It is not rich in natural resources, but it has enough to get by and can trade with Germany or the Soviet Union for the resources it needs. It does not have exceptional military leaders, but there are sufficiently good high-rank leaders which should be capable of leading Turkey's army. The main disadvantage of Turkey is its isolationist, democratic policies after the death of the Great Turk, which make it difficult to plunge into war without a huge dissent hit. It s research teams, while not top-of-the-line, are decent.
Since you only have two research slots, it would be best to focus only on the absolute necessities. You can keep one slot open for industrial research and use the Turkish Petroleum Company for machine tool research -- since you have a low IC base, any additional gains in IC are sorely needed, even if the technology required to achieve them is one year in the future. Istanbul Military Industries are very good for infantry and cavalry research. Around 1937-1941, you should start to research your land doctrines. Generally, you should do this as late as possible and aim to complete the research just before going to war so you can research more immediately important technologies first. You may wish to invest in more improved bombers and fighters if you have an extra slot that you can't do anything more productive with, but you can also requisition some planes from the Soviet Union if you are allied with them (a group of four tactical bombers should be enough to achieve your goals).
As long as you can give metal, Germany is a good trading partner for most of your resource needs. The Soviet Union would also be a good choice, and the sooner you can get an alliance with either Germany or the Soviet Union, the better. However, an alliance with Germany can get very risky. You cannot stand alone against the United States in the Middle East, and you can be crushed if the Allies decide to attack you from North Africa. The Soviet Union is a much better choice for an alliance. You should first reinforce and upgrade everything before producing any units. Don't bother producing 1918 infantry at the start -- if you have extra time before you research basic infantry, just stockpile on supplies, which you can later stop producing if you have a sufficient quantity. You should aim for 2 parallel series of 12-15 infantry units each at the start. when these are produced, you should deploy them to Istanbul.
By the time Germany declares war on Poland, you should try to have an alliance with the Soviet Union. Your army should be substantially better than both Greece's and Bulgaria's. Wait until the Vichy Regime event triggers, then declare war on Syria. You can move your army (you don't need more than one division) into Syria and Lebanon unopposed, and you can annex them quickly. Next, you can invade Bulgaria and Greece via Istanbul, as long as you make sure no wacky declarations of war result, pitting you against Germany or the United Kingdom. With Soviet tactical bombers to mow down enemy troops, this should not pose a challenge. You can go wild in Eastern Europe, and can even conquer Yugoslavia and Romania and Hungary, if they are not allied with Germany.
You will be unable to defeat Germany military, and the same goes for the Soviet Union. However, the Soviet Union will frequently declare war on Germany in 1942 or afterwards if Germany has not declared war on it yet, and it will proceed to take a pounding. To protect against this eventuality, a minimal defense plan would be best. Leave Eastern Europe to Germany and concentrate a significant contingent of troops in Istanbul, Trebizond, and Kars. Start building forts there like mad, and you should be prepared to successfully defend Istanbul very early on, and should be able to defend your northern border by the time German troops get there, in around 1942/1943. Just wait patiently until the Soviet Union launches a counter-attack or the United States or United Kingdom lands troops in Europe for your chance to go on the offensive. When the chance comes, you should be able to reclaim your lost territory with significant interest.