The general plan of our drill sequences is:
1) Get your core body doing the right things.
2) Add arm and leg movements.
The reason for this approach is that arm and leg movements can be used to mask a multitude of swimming errors. If you haven't learned to be balanced in a horizontal position, for example, you can cover it up by doing frantic kicking.
The central position for freestyle swimming is what we call the skate position. When you are in this position, your body is really like a teeter-totter floating on the fulcrum of your lungs, and your head and leading arm balance the weight of your legs on the other end of the fulcrum. The two factors that control whether you are in balance are:
1) head position - You want to relax your head into the water with your nose pointed down. If you lift your head to look forward, your hips will tend to sink.
2) leading arm position - You want your wrist to be lower than your shoulder, and you want to keep your wrist relaxed with your fingertips angled slightly down. If your leading arm is too high, this will also cause your hips to sink.
The ideal skate position can vary from swimmer to swimmer depending on a number of factors (like their natural buoyancy), and it may vary for the same swimmer over time. When I first began using the Total Immersion approach, for example, I needed a lower leading arm position to bring me into balance than I need now, and I'm pretty sure the reason is that in the early days, I was compensating for other things I was doing wrong, but now those other aspects of my stroke have improved and I don't need to compensate as much.
So I'd suggest experimenting with your skate position and finding the head and leading arm position that are ideal for you (which allow you to keep your hips up with a minimum of kicking), ingrain that ideal position (on both sides), and then practice spearing directly to it each time you take a stroke. If you can learn to keep your hips up through balance, then all of your arm and leg movements can be directed toward propulsion, which will allow you to move faster using less energy.
Be aware that the main thing your kick should be doing is to counterbalance the rotation of your core body. Your kick (particularly in distance swimming) is not a major source of propulsion. But you may benefit from spending some time improving your kick. The best drill for this, in my experience, is called vertical kicking: Go into water that is over your head, fold your arms across your chest, and keep your head above water by kicking. Focus on kicking from your hips and ankles - not from your knees. You can transition from this to horizontal kicking by starting vertical kicking and than letting yourself "fall back" onto your back while still kicking. If you spend a few minutes doing this every time you swim, your kick should gradually improve, and you should end up with a narrow, streamlined, hip-driven kick.
Let us know how you make out!