Brain-training apps mostly make you better at brain-training apps. What builds real cognitive reserve is learning things that are hard and new: a language, an instrument, a skill. And the single best-evidenced brain exercise is aerobic exercise, which grows the hippocampus and raises brain blood flow more than any supplement.
Does any of it work?
Yes, some of it, and the useful distinction is between exercising your brain and playing games that look like exercising your brain. Practising a task makes you better at that task. The question is whether it transfers to anything else, and for most brain-training apps the honest answer, backed by a large 2014 consensus statement from dozens of researchers, is that it mostly doesn't. You get very good at the app.
Use it or lose it, sort of
The underlying idea is sound. People who stay mentally active through middle age and beyond tend to decline later and more slowly, and the theory is "cognitive reserve": a brain with more connections has more to lose before anything shows. What builds reserve is learning things that are hard and new, not repeating things you already do well.
The apps
Lumosity paid a $2 million settlement in 2016 for claiming its games prevented cognitive decline. That's the state of the evidence. The games improve performance on the games and on very similar tasks, and the improvement fades when you stop. If you enjoy them, they're harmless. Just don't mistake a high score for a healthier brain.
What actually builds reserve
Learning a language, which engages memory, attention and pattern-finding at once. Learning an instrument, which does the same with motor skill added. Learning a physical skill with a mental component: dancing, a martial art, a sport with tactics. Reading demanding material and discussing it. Taking a class in something you're bad at. Teaching someone else. The common thread is difficulty plus novelty; the moment something becomes easy it stops building anything.
The body part
The single best-evidenced brain exercise isn't mental at all. Aerobic exercise increases blood flow to the brain, promotes the growth of new connections in the hippocampus, and in trials on older adults has actually increased hippocampal volume over a year. A brisk walk does more for memory than any app and more for blood flow than any circulation supplement, which is worth remembering on a site about one.
The rest of the picture
Sleep, because learning that isn't consolidated overnight is lost. Social contact, because conversation is one of the most demanding things a brain does. Stress management, because chronic cortisol shrinks the hippocampus you're trying to build. A decent diet. Managing blood pressure. None of it is a brain exercise and all of it is the ground the exercise stands on.
Where Memocept fits
As an optional extra to all of the above, at best. It doesn't build connections; it's a small dose of circulation amino acids. If you're doing the walking, the learning and the sleeping and want to add a caffeine-free capsule, there's little harm for a healthy adult. But an hour of Spanish a week will do more.