Bang for your buck and proven results wise, there’s arguably no better supplement than Creatine Monohydrate. Ignore the loading phase, it’s not necessary and reap the rewards of adding creatine into your supplement stack. Make sure to drink plenty of water as creatine can cause dehydration as it pulls water into muscle cells and you’re safe to use in the off season as well as on prep. It’s legal, it’s great for most trainees and one that almost all professionals will recommend use of to some extent.
They do them both in tablet and powder form, dependent upon how good you are at swallowing pills, the pills can be more convenient. But each to their own on that one.