If you have no idea what you like: buy a bullet, and keep it cheap. It answers the only question that matters at this stage, which is whether vibration does anything for you, and you will keep using it even after you own bigger things.
If penetration has never done much for you: stay external. Most people who have a clitoris need it involved to finish, and a toy that only goes inside is solving a problem you may not have.
If you have tried a vibrator and felt nothing: change the technology, not the strength. A pressure wave toy feels nothing like vibration. That switch works far more often than buying a louder motor.
If you share walls: check noise before power. Anything is quiet on its lowest setting. What matters is how it sounds on high, and a hard nightstand amplifies it more than the toy does.
On material: silicone or ABS plastic, nothing jelly. Both are non-porous and clean properly. Jelly and soft TPE hold onto bacteria no matter how you wash them.
On power: rechargeable, not battery. Rechargeable motors are stronger and quieter, and they do not fade as the charge drops the way a battery toy does for its whole life.
Still deciding: the best beginner vibrators walks through specific picks, and dildo vs vibrator covers the other question everyone asks first.