Hi and welcome!
Lantus is good. 2u is a higher dose than we usually recommend starting with - we like to start at 0.5 or 1u and go up in slow increments after letting each dose change "settle" for a few days. I assume you bought the vial (10ml)... we actually recommend buying the OptiClik/SoloStar pen cartridges... it is basically 5 small vials of 3ml of insulin. It's more expensive upfront but cheaper in the long run because you can use all of the insulin in the pens, whereas the vial tends to go bad after a few months, even if it's handled properly and kept in the fridge, so you're just throwing away $$$!
However, Hills m/d is higher in carbs than what we recommend, so it will probably counteract the 2u of insulin. I believe it is around 13% carbs.... we recommend less than 7%. Less carbs = less need for insulin, so don't change the diet until you are testing at home and can see how the numbers are changing.
Janet and Binky's list has the carbohydrate values on some common foods. Just pick one you can afford and your cat likes! You can also feed more than twice a day - unregulated diabetics can't properly process the food they're eating (why weight loss is a common sign) and so they are very hungry all the time. Eating twice a day is no fun for a human and a cat's metabolism is twice as fast as ours! 4 meals a day is a good number for most, though some do more. You don't want to feed within 2 hours before each insulin shot, so that your preshot blood glucose check aren't inflated by food.
You don't need to take your cat in for a curve at the vets. This is a waste of money and often leads to the vet prescribing your cat too much insulin. Vets, as we know, are high stress environments, and stress can make your cat's blood glucose skyrocket up 100+ points. It even happens to non diabetics. So when the vet does the curve and sees nothing but high numbers, he automatically says "give more insulin!" but when you get your cat home to his comfortable environment his numbers drop back down, and now you're shooting that big dose into lower numbers... very dangerous. So save that money and put it towards buying a glucometer to test at home.
As far as home testing goes, we use human glucometers and poke our cat's ears just like human diabetics poke their fingers. Any human glucometer with cheap strips (the biggest expense of treating diabetes) - Walmart's Relion Confirm and Micro are two cheap and easy to find meters. Avoid the Freestyle Lite with the butterfly on the strips - these don't read over 300 for some reason on cats.
Feel free to ask as many questions as you want, there are lots of people here to answer
