Starting solids always sounds weird ah - lets just say starting food. There IS SO MUCH information out there. Some of it contradictory, lots of it possibly sponsored by companies - making it hard to know what to do.
But the main thing you need to remember is as long as you are getting in as much unrefined/unprocessed stuff (aka vegetables/fruits/grains/meats) in as you can then that is all that is important.
When we start with 'solids' and food lets just focus on real food. Stuff that is probably just grown and washed and then purchased by you. Easy - old school way to eat but the best way. Fruits and Vegetables are full of everything we need - adding things like small amounts of fats (olive/coconut oil or ghee) can help with absorption of fat soluble vitamins.
I have attached a Starting Solids form to this blog that may be helpful for you. You can write what day you started the food and if anything popped up from your small human consuming it. Could be stuff like - excess gas, irritable, upset stomach, rash etc. It can help you see if there is a pattern. If anything does come up (like a small rash or loose bowels) this does not mean this is an allergy, Food reaction and Allergies are very different. (Allergies are life threatening and need medical assistance immediately. Allergies often close airways, cause swollen tongues etc)
Your baby is new to eating, this is brand new for them and their digestive systems are getting used to processing 'real' food so expect that there will be a change in their bowel motions and also their mood. But with the chart you can jot this all down and see if there is a pattern etc.
Any questions though just ask!