As a student cooking for one, and some days not eating meat, I need more simple, healthy sauces that can work well with a mix of veggies and pulses. They should also freeze well. I've been using herbs with tinned tomatoes too often; can you suggest other sauces to try?
Nigella says in her book Kitchen "It's always worth having up your sleeve some quickly got-together sauce or dressing". In Kitchen Nigella has 3 suggestions for her favourites - Salmoriglio Sauce (a garlicky mixture with fresh herbs), Jumbo Chilli Sauce, and Parsley Pesto. She also suggests a very useful Blue Cheese Dressing which is wonderful with most salad leaves and as a dip for vegetables. The recipes include keeping instructions for each sauce.
If you have a jar of mayonnaise in the fridge then there are some easy stir-together sauces in Nigella's book Christmas - Honey-Mustard Mayonnaise and Beetroot and Horseradish Sauce (you could use mayonnaise instead of creme fraiche for this sauce, if you like). You may prefer to make these in smaller quantities as the recipes on the book are intended for larger gatherings but they are very easy to scale down. Both of these would be good with steamed or roasted vegetables and some salads made with pulses.