If you're very active, and in training for a half marathon, then you may well need more carbs than I do, but that should be covered by your insulin. You should speak to your diabetes nurse about balancing your insulin with your carb intake and exercise levels. Ask for help in working out your correction ratio (how much one unit of bolus reduces your BG).
Ask if you can be referred to a DAFNE course, as this really seems to help people.
You should aim to test before eating, and then (to begin with) at 1 and 2 hours after eating. That way you will build up a picture of how various foods affect you. When you are confident about your reaction to carbs you can drop the 1 hour after eating test, and just test at 2 hours (although if your meal has a high fat content you may need to test at 3 hours, as fat will slow down carb conversion to glucose). You should also test whenever you feel "odd".
I'm still in my honeymoon period (diagnosed in November last year) so my insulin needs are quite low, but my BG levels are usually around 4.7 on waking, and about 5.5 after meals. I aim to be at around 6.1 at bedtime. My levels are perhaps a little on the low side, but I've never had a serious hypo, and I have good hypo awareness.
My normal diet is a small bowl of porridge with a few raisins and flaked almonds, 100ml of orange juice and a coffee for breakfast, a portion of meat or fish with plenty of vegetables (but no potatoes, rice, pasta or "stodgy carbs") and a small glass of red wine lunchtime, and homemade soup, 40 grams of homemade bread, salad, cheese, yogurt, a small fruit and a small glass of red wine in the evening, and sometimes a small glass of milk and half a digestive at bedtime if I'm not at 6.1 before turning in.
If eat out, have friends round to dinner, or spend an evening in the local bar, all of the above goes out of the window, but I correct before and/or afterwards with enough insulin to make sure that I am never above 8.5.
I'm 5 ft 8, weight 9 stone 6 and fairly active but not really what you would call sporty.