knitgal’s advice is good. Casting on looser should definately help with that first row, which is always the hardest.
I’ve been knitting a long time and am still not sure what all the factors are in tight or loose knitting. But I was observing recently while I knit and noticed this… if I pull hard, or apply a lot of tension on the wrapping yarn it will make it tighter. Try to consciously keep that looser, and that may help.
Another thing is just to keep going. I find that new knitters often knit tightly and loosen up later. One of my present students started off very tight, I had her do a gauge swatch for a project and she needed, I think a US #9 needle to get a normal gauge. But now she is back into the project, after side tracking to a scarf and hat and I notice her gauge is way loose, but I don’t want to discourage her by making her start over, so the 0-3 month sweater will just be a bit big. LOL