Eating a low FODMAP elimination diet is difficult but so worth it. I have been eating low FODMAP for almost 3 years now and I am more than willing to answer any questions you have. I manage by cooking everything from scratch since I have a few odd food allergies on top of food motility issues.
As far at what you should and shouldn't eat my favorite source of information is form Monash University in Australia. They have tested the type and levels of the sugars in various foods. They have even tested some permies favorite foods to grow.
The phone app is great. It not only tells you if it is high in fructans but it also tells you what class of sugars it is high in. They updated with new foods when they have tested them. It has a great list of fruits and veggies. I have tried quite a few new veggies and even altered my gardening thanks to the app.
Let me know what kinds of foods you eat and what you are having a hard time swapping out? I may be able to help find alternatives.
Garlic infused olive oil and the green part of bunching onions are the best ways I have found to add those flavors to any recipe. I tend to use lots of green cooking herbs that happen to also be perennial in my garden along with the bunching onions. Lovage and celeriac are good celery replacements in soups and stews. I use rice flour for sauce making and rice noodles for pasta.
Watch out for things like dextrose and locust bean gum in ingredient lists. These types of food additives aggravate my symptoms in even small amounts and they are in everything.
Good luck and let me know if you have more questions.
If you are eating out steak houses are the easiest to find food that doesn't have garlic and onions in it. Sushi is another easy meal. Chinese restaurants will cook your food without any sauce if you ask.