If your looking to lose weight, 100% diet. You can lose weight without exercise just by cleaning up your diet. If you want to get stronger, you need resistance training and if you want to get fitter you need conditioning, obvious i know, but so many people complicate this, killing themselves in the gym for little reward. Just some guides, to build strength train 1-5 rep reps you will also add a bit of muscle. To build muscle train 8-12 reps, but the weight will be lighter hence less strength. Be clear in your goal, Dan John has some great material on this, the first exercise he makes his athletes do is the squat, biggest bang for your buck. Re supplements many are a waste of money, read carefully. Most important of all you need recovery, if you don't recover properly you get weaker not stronger