I recommend merging armies / navies instead of attaching. Attaching should only be used for mercenary regiments (as they cannot be merged), or if you want to attach to an ally / vassal army for some reason.
Ottomans are a nation focusing on land conquest for a long part of the game. Going for colonization (exploration/expansion ideas) is not recommended in the beginning. It might be feasible after you reached the Persian gulf (Basra) so you can get to South-East Asia. For a beginner I would even suggest to not do colonization with Ottomans but better focus on conquering your neighbours on land. As Ottomans you are very strong and you are also in the conventient positon to have multiple routes of expansion. I see that you focused most of your conquests on Europe. I suggest that you should conquer land from the Mamluks and Qara Qoyunlu. This is valuable to get more trade = money, especially the Mamluk provinces are of accepted culture and religion, so they are not very rebellious and give you a lot of benefits.
If you want to try out colonisation, Castille is probably the best nation as a beginner. Their position is much better to get to the Americas. Colonizing the Americas is easier than Africa or South East Asia as the natives rebel less and are much weaker. The nations there are also much weaker and easy to conquer. You might also get Cristobal Colon via event as an Explorer with 6 manoeuvre which reduces attrition.
Ottomans are a nation focusing on land conquest for a long part of the game. Going for colonization (exploration/expansion ideas) is not recommended in the beginning. It might be feasible after you reached the Persian gulf (Basra) so you can get to South-East Asia. For a beginner I would even suggest to not do colonization with Ottomans but better focus on conquering your neighbours on land. As Ottomans you are very strong and you are also in the conventient positon to have multiple routes of expansion. I see that you focused most of your conquests on Europe. I suggest that you should conquer land from the Mamluks and Qara Qoyunlu. This is valuable to get more trade = money, especially the Mamluk provinces are of accepted culture and religion, so they are not very rebellious and give you a lot of benefits.
If you want to try out colonisation, Castille is probably the best nation as a beginner. Their position is much better to get to the Americas. Colonizing the Americas is easier than Africa or South East Asia as the natives rebel less and are much weaker. The nations there are also much weaker and easy to conquer. You might also get Cristobal Colon via event as an Explorer with 6 manoeuvre which reduces attrition.