The best advice I can give is to seek a path to specialize in. It might seem counter intuitive to narrow your scope to a specific realm of fitness but you’ll increase the amount of business that will come to you. With basic certifications you are able to guide a wide range of people through workouts, however so can everyone else with a basic certification. You need to find away out from the crowd so you can stand out and offer something that fewer trainers can. Once you are more specialized you will find that more people will seek you out rather than the other way around. Think of it this way, if you are a trainer that specializes in marathon prep/training you are narrowing yourself toward that field. However, if you were someone wanting to train for a marathon would you seek a run of the mill trainer or someone who specializes in what you are training for? Obviously people will want to find someone that can meet their specific needs. So in the long run although you are narrowing your scope you will find more clients willing to seek you out and pay more for that specialization they cannot get with any other trainer. Just find out what interests you the most or where you have the most experience and capitalize on that.