Ask your doc to put you on a DAFNE course, where you'll sit down for a week with a few other diabetics, a dietician and a DSN, and they'll talk you through the whole carb counting business. There's usually a long waiting list, though, so
@catapillar 's bertie suggestion is a good starter for ten.
We can't give dosing advice here, but DAFNE guidance says as a general rule 10 grams of carbs will raise you by 2 to 3 on your meter and 1 unit will lower you by about 2 to 3. They'll normally say try 1 unit for every 10 grams you eat, works for a lot of people, but not all, I tend to need about 1.5 for each 10g, others will be more, others less, so it's a case of experimenting.
Next time your levels are fairly stable, try eating 10 grams of carbs without any insulin, wait for an hour and see how much you rise by, will likely be between 2 and 3. Likewise, try 1 unit without any food, and see how much you drop by (don't try this if you're already too low). It'll give you a rough idea of how much insulin is needed to counteract food. In an ideal world, if you were eating 50 grams, it would be 5 units, but in reality, it might be more or it might be less, and you won't really know until you figure out how you generally react to 10g and 1u.
Remember that it's not the total food weight, just the carb content. 100g total weight might only contain 10, 20, 30, 40 g of carbs depending on the food, so look at the labels on the back of packets.
If it was just a case of balancing carbs and insulin, it would be really easy, but there's a lot of background stuff going on which can throw things out. Even the number of times you chew food can affect it: chew a lot, it'll be broken down quicker and end up as glucose quicker, chew less, it'll take longer, so you could end up with food still breaking down after insulin has reached it's peak.
Exercise is a major thing. Generally, the more exercise, less insulin. So if you're planning on taking a four mile walk after lunch, you might want to think about taking less lunch insulin.
Your liver will release and also take back glucose with a mind of it's own, so if you get different results with the same food/dose two days running, you've not neccesarily got it wrong. It could just be the liver or the hundred and one other random factors throwing a spanner in the works. A lot of people cut themselves up about what seem like mistakes when the reality is that there is random stuff going on.
Testing reactions ain't that easy with strips because they're just snapshots. Have a look at the Freestyle Libre, which measures continuously and shows a graph of where you've been and predicts where you might be going - a bodily GPS! I've been T1 for almost 30 years and have learned more from it in a few months than in decades. Costs £100 per month if used full time, but many use a single sensor at £50 for two weeks every now and then and find it useful for some basic insights. I'm convinced it'll be on the NHS eventually.
None of this will work very well unless you're basal is correct. A rough and ready way of checking is to wait until about six hours after your last meal/insulin and then sit about, don't exercise, put a box set on the telly, and just watch over the next six hours to see whether you stay level or go up or down. If basal is right, it should stay around the same level. Easy to do with a Libre (just look at the overnight graph when you wake up) but still do-able with strips.
The DAFNE people can be quite insistent that you only correct at meals but, with Libre and cgm, there are good arguments for correction doses between meals. There is no harm in seeing what 1 unit does to you if you're at 12. But remember if you've still got insulin in you from your last meal, it'll be working for about 5 hours in total, and can give a surprising drop in the last hour or two, so sometimes it's best just to wait. Libre's useful for that - it shows an arrow pointing downwards when you're dropping, there's been a few occasions when based on a strip test, I've been thinking about a correction but then I can see from the arrow that I'm heading in the right direction, so have just left it.
You'll get the hang of it eventually. It's an art more than a science. Just gone 12:30 now so I'm heading off for the set lunch menu at my local Indian, two poppadoms, fish pakora, lamb jalfrezi, no rice, and the crispier bits of a naan bread. The lchf guys would put me up against a wall and shoot me for that sort of sacrilege, but I mention it only to point out that that sort of meal is easily do-able once you get carb counting and some knowledge about personal responses under your belt.
Good luck, you'll get there!
