Get your foot in the door and get a feel of what you'll need for the projects that come your way. It's an interesting phenomenon in this business when starting out how work finds you. You may have designated a market to go after and that's what you want to do but later find that different sorts of projects come your way on a regular basis.
For example, you might want to only do clearing jobs and find that after the first clearing job a person, maybe a neighbor, wants you to build a pond. You take the job and find out you're good at building ponds. You take the first pond job and the customer is happy and they tell their friends. Next thing you know you're a pond builder. Sure it includes clearing and grading but it's a specialty you might not of thought of. I know it's a simplistic analogy but it's how this business works and the cool part is there are many different aspects to exploit in the realm of excavation.
Commercial, residential, industrial, farms, land, etc. There is all sorts of niches out there to be had and if you find the right niche it can be profitable and allow you to reach your goals. Work hard and preserve your cash, don't over extend yourself with equipment payments in the beginning until you have the work load to make those monthly payments, as the come regularly, regardless of work flow.