You are definitely not behind, don't worry.
Would it be more helpful for you to follow a set plan? If so, I agree with getting something like the Annabel Carmel book or even the free weaning guides boots will give you for example. They have a really detailed set out plan with week 1 give 1 spoonful of carrots, day 2 3 spoonfuls of broccoli etc until you build up to full meals with recipes.
Or would you find reassurance that a wing it approach is ok more helpful? That's what I've done with my three. I mostly followed baby led weaning, so when the baby can sit with support, get items to mouth and shows interest in food, I have looked at what I'm eating that they are interested in and let them have some bits for themselves, but only to feed themselves. For example I have just started with my third baby and so far he has had
Steamed carrot stick
Lick of mashed potato
Rice - I just put it in clumps on his tray and let him squash it, not much got to his mouth but he enjoyed it
Cucumber, roughly peeled and cut into sticks
Banana broken into thirds
Orange segments with end bitten off (I did hold this to prevent him swallowing it)
A chip, no salt
Toast fingers or triangles, with butter
Pasta with butter (he just sucked the butter off)
Plain Greek yogurt - I dunked the spoon and let him hold it.
It's all about exploration and experiences at first, you don't need to worry about what they are eating as they still get 99% of their nutrition from milk. If you really want to you can get into looking at what nutrients are in different foods but I don't worry about that kind of thing, I just think about what is suitable in terms of is it possible for him to hold it in his fist with enough sticking out to get to his mouth, and is it fairly soft and not likely to hurt his mouth (like say a ryvita would be too hard and scratchy).
With the other two, it started off sporadic which is what I'm doing with DS3 now. Some days he'll eat twice in one day, sometimes it's 3 days between him being offered any food. It's really just a fun activity for him right now and I don't want to overload his system. In my experience they let you know very clearly when they are ready for something more regular, and at that point I'd start buying food with him in mind specifically and thinking about what I can give him. It's likely that one meal will fit best into your routine at that point so start with that one.
DS1 I did completely BLW until he was on normal food and then by the end of the first year I was a bit bored of the mess so spoon fed him anything like chili, stew, etc. DS2 never really liked BLW but I still started off that way and then moved to more spoon feeding once he was showing me signs he wanted to eat more regularly. He was keen for breakfast, so then had Weetabix every morning for ages. Breakfast is a nice easy one because you don't need it to be varied. I'm not sure which way DS3 will go, he loves the self feeding, but I did like the baby porridges and such so I'll probably try him with some things like that soon. However lunch seems to be the time he's most awake and eager so I think that might be the first regular meal he has.
Ultimately it doesn't really matter. Don't start before 17 weeks, don't wait longer than 8 months, limit salt and added sugar, avoid honey, avoid choking risks and whatever else you do within those guidelines is likely to be absolutely fine.