The question assumes there's a best way. There mostly isn't.
Adult learners obsess over method because we're anxious about wasting time. So we research: Fingerstyle vs. strumming, classical fingering, the YouTube channels with the highest production value. Then we do three weeks of perfectly-selected practice and quit because it feels like work.
The actual best way is the one you'll do every day for a year. That's it.
For most people, that means:
- Pick songs you want to play, not exercises that "build foundation correctly." Yes, your technique will be rough. It'll also be *real*, tied to music you care about.
- Get a decent used guitar for $100-200, not a $40 Amazon plank or a $600 investment that feels like a financial commitment you have to justify.
- Ten minutes a day beats two hours every three weeks.
- The point where you quit is usually month 2-3, not because the method failed but because the novelty wore off and you hit the wall where your fingers hurt and everything sounds bad. Push through that wall. It's 2-3 weeks.
The people who learn guitar as adults are the ones who treat it like a hobby, not a system to optimize. Give yourself permission to sound bad for a while.