Which GDPI course should I opt?

Hey guys, I got 91.36%ile in CAT (no hopes from XAT). I'm GNEF, with 9/9/8 profile. Hoping some calls from decent Colleges like IMT-G, IMI-D, FORE. Which GDPI course should I opt for? Also, can the preparation be done without any course? I don't want to take any risks, I can afford a course so no issues in that... but I just wanna know if it's even worth it? Please give me some advice and suggestions.