切尔克西亚 starts with - 2 diplomatic relations penalty due to its government form so starting position is really crucial for Circassia. Your short term goal should be government reform as fast as possible.
Due to weak starting position and being Orthodox in the middle of Muslim land, alliance choice is often limited to 拜占庭, 特拉比松, 格鲁吉亚 or 伊梅列季. It's advised to avoid alliance with both Byzantine and Trebizond as they often fell Ottoman early on and you don't have the power to defeat them yet.
Your ultimate alliance is either 莫斯科, 波兰 or 立陶宛. Your starting point is usually won't allow you to do this but keep one slot open for them. Instead, fabricate on Imereti as soon as possible and declare on them. You can win alone but you could also promise land to Georgia to help you out. After defeating Imereti, take one province and vassalize them, betray Georgia to free your slot. Sooner or later, Ottoman will declare on you and Georgia often betrayed you anyway.
After that, you usually can have alliance with your ultimate alliance and focus on high developed province. Declare on 克里米亚 if they are not vassalized by Ottoman yet, 金帐汗国. Keep your relation high with Genoa as they are the source of your instituion spread. Try to have a border with your ultimate alliance. Keep your relation high with Muscovy as they will have permanent claim on all of your pontic steppe area.
If you already have enough favor from your alliance, try to attack Ottoman ASAP You don't want to get sandwiched late in game between your ally, Ottoman and Persia. And Ottoman is the biggest threat as they usually desire Adyghe