Unfortunately there is no magic recipe or combination, because it depends on your language pair, specialty fields, country of residence to some extent, though in our trade that is becoming less of a factor.
There is a little bit of market research to do to start with, also a bit of gambling, or trying out and see what works and what doesn't work as well. If you're afraid of uncertainty, definitely freelancing might not be a good idea for you. A possibility to balance risk taking is to have a part-time job on the side to pay the bills when downtime comes. But markets and technologies being in constant evolution, new opportunities may also present themselves, opening new horizons you hadn't thought of before.
But the bottom line is to regularly assess your situation and see what you can do to grow your freelance business in a way that serves what you're trying to accomplish. In that respect setting goals is key, then evaluating the success of each component of your business. If you have several specialty fields and one of them is not profitable you may want to drop it. It is OK to make mistakes, that's how we learn and grow. Of course one of the difficulties many freelancers encounter is to learn to do their own promotion. Many start in this profession thinking all they have to do is settle in their ivory tower and translate.
Dang. We also need to promote ourselves, preferably in a non invasive manner, and to be a business person.
- Some translators narrow it down to 1 unique specialty field, a niche. A good way to go if the specialty or the language combination is rare or in high demand.
- Others prefer to diversify and offer multiple services, but that should never be done at the expense of quality.
If you want to diversify, open an additional "aisle" to your freelancing business, the first thing I'd say is choose one you do well, and that you enjoy. Then study the competition and see what you can offer that others don't in order to stand out.
Then promote by showing what you have to offer and most importantly how it will serve your potential client.