Started mine on toast & a lick of marg or just toast (they make it pretty soggy in no time and any spread is very messy) at 6 months or so. As soon as gluten was OK really.
DDs first weaning was a rice cake at 5 months. Lazy mother knew I was starting her on baby rice a couple of days later and wanted to keep her quiet while the rest of us ate. She is now 8 months and has something suitable off my plate every mealtime - tagliatelle last night, peas the night before.
I tried finger food from about 8 months - starting with toast and bread, moving on to things like cooked carrot and broccoli and meatballs. dd choked a bit at first but got used to it quickly (just as well, by 11 months she wanted only finger food). I avoided marmite till 12 months.
I don't think presence of teeth or not makes a lot of difference by the way.