Finally upgrading to a 3BHK, feeling overwhelmed by hidden costs

Visited a few 3BHK projects near Kalawad Road and Mota Mava last weekend. My wife wants a bigger space for the kids, especially with school admissions coming up. Builders like Maruti Group ke rates dekh ke lagta hai, negotiation kitna possible hai? Is it 2-3% or more? Also, possession ke time pe kya kya hidden charges aate hain, like maintenance, utility connection, PLC adjustments? Honestly, it's so confusing. Mera budget around 80L-1Cr hai for a 3BHK. Rajkot mein end-user ke liye kya best negotiation strategy hoti hai? Don't want any surprises when the final bill comes. Kisi ke paas koi real-world tips hain to share karo please!