Starting strength routine to get fit using weights
f you prefer to go to the gym instead of training using your body weight outside or at home like shown in this post the 5x5 routine might be a good fit for you. Crossfit and marathon training plans usually incorporate advanced workouts, which are not a good fit for beginners.
Crossfit uses a lot of pull ups in their routines. You might feel like you have to do a little work before you embarrass yourself in front of a group. The 5x5 schedule can be done without any help and at any time without having to attend a class. Pros are the simplicity of the program and quick progression with direct motivation as you lift more in every workout. A downside is that the equipment has to be either bought or gained access to by a gym membership.