Swimming is a big thing for me matey, t'is one of only a handfull of things I can do well ..
Anyways just picking up on summat Pax said ...
Free Style (front crawl) with alternative breathing is best if you want to keep your strength balanced. That is breathe left, miss one, breathe right, btw.
Reason for alternative breathing being important is that whichever side you breathe on the opposite arm will naturaly do the most powerfull stroke so as you can get a longer breathing space.
Like if you breathe on the right all the time the left arm will work far harder than the right arm and verse-vica?
Sacrificing every third breath also means that on every third stroke you have the best aquadynamics (always faster head down?) and neither arm needs to provide the extra pull to rise you up to breathe. You get more speed, and thus distance, for less energy using that technique.
M'final tip (with apologies if I'm teaching granny to suck eggs) is to learn to time the outbreath so its all gone, but only just all gone, by the time your head comes up to breathe. That way none of the time your head is spent out of the water will be wasted blowing out and you get a far longer chance to suck air in.
Best work out of all tho' is simply to jump in and thrash about 'doggy paddle' style with your head up all the time. You'll be completely
cream-crackered after just a few lengths that way!