I went through this process in August and September.
The order in which I did the challenges are below.
I reacted mainly to lactose so I stick now to lactose free milk and yoghurt. If I have more than 1 piece of bread a day and/or pasta for a meal I have constipation. Large amounts of garlic, onion and stone fruit also cause problems. If I keep eating small amounts though, with a day's break between each, I can manage.
Please see an Accredited Practising Dietitian about a low fodmap diet. The challenges can be complicated but the process is worthwhile to work out what what to eat to feel well.