Since after the contest the federation here in Greece will demand bloodwork from all participants I ll have to be extremely cautious about what supplements to use..
If you're planning to lose 7-8kgs in 10 weeks, you will need to be very strict with your diet and training. I would focus primarily on nutrition to obtain a hard and lean physique. There are some supplements that may help marginally, but 98% of your appearance and success will be determined by your diet.
As far as natural supplements go, I would definitely read up on GDA products. These products can help with nutrient partitioning, which can help your body better utilize carbs. Using a product like Slinmax would be beneficial by allowing you to keep carb intake higher while not suffering as much from bloating and water retention. Slinmax can also help with muscle fullness and pumps, which are both keys to looking lean and hard for a show.