Supplements are not totally necessary to increase strength, but some definitely help. StratFit is going to ensure your training is on point, you need to lock your diet in.
good multi-vitamin, and a whey protein isolate powder.
The vitamin should be taken once or twice per day with food, and the protein before and after training 20 to 25 grams per shake. If your budget permits, creatine monhydrate, arginine (nitrous oxide booster) and amino acid tablets/powder are also good to put in the mix.
Natural testosterone booster like vitamin d3, ZMA, Tribulus Testeris, MACA, and Horny Goat Weed are good idea for men over 35.
The important thing to remember is: get your training and whole-food diet in line first. This is fundamental.