What should a beginner at the gym buy first?

Most people start with whey protein to reach their daily protein, then add creatine once training is regular. Pre-workouts and amino acids are optional extras.

Can I stack creatine, whey and a pre-workout together?

Yes, they are commonly used together. Check the pre-workout label first, because some, like MB WrathX, already contain creatine, so you may not need a separate scoop that day.

Should I take sports supplements on rest days?

Creatine works best taken daily, rest days included. Protein is useful on any day you fall short from food. Pre-workouts are only for training days.

Are sports supplements only for bodybuilders?

Not at all. Runners, footballers, cyclists and trekkers use protein for recovery and electrolytes for hydration. Choose based on your sport and how hard you train.