Gaurav I am also trying to learn how to find out Ishta Devta from morning I have found in my searches some understanding based on that I find that in your horoscope Jupiter is having 327 degrees so this should be strongest planet I am not sure though and in your Navamansha Chart Jupiter is placed in Gemini Sign The house just before it which should be able to tell ur Ishta is actually empty and on some other thread I read if this is the case then the house 2nd from Karkmansa should be read which is also empty in your case
In this case I am not able to understand when the houses are empty then how do we decide the Ista Devta ??
Is it the lord of Rashi just before the Karkmansa in your Chart which in your case is Vrishabha and its lord is Venus whose deity shoukd be Durga Ji
If I am not wrong but Gaurav don't take my advice at all seriously because I am not at all sure of this analysis that I have done,
I am posting it so that if some one replies to your question I will also be able to understand what mistake I have done or I have done it correctly or not.