K.W.
Baby food is what anthropologists call a "socially acquired need". Babies don't *need* baby food. They just need food that can be eaten without teeth. If they need the dead-smooth consistency of commercial baby food, they're probably not ready for solids yet. Babies are ready for solids when their protective gag reflex calms down and they express an interest in eating. This can happen anywhere between 3 and 15 months.
A few things my babies liked:
avocado, mashed with a fork
banana, mashed with a fork
rice cereal
milled puffs
Veggie Booty
I always let my kids feed themselves at home. I'd generally skip the plate or bowl (they tend to throw it), and just put a pile of food on the high chair in front of them. This presumes, of course, that you have a high chair tray that can be removed and scrubbed well with soap!
Put a small blob of food (1-2 tablespoons) in front of the baby in the high chair and let them have at it. If the child finishes it and seems to want more, give them more. Expect to give the baby a bath after every meal!
When we were out and about, I usually fed the baby sitting in my lap and focused on much neater foods. I mostly did the puffy foods that dissolve in the mouth: Veggie Booty and millet puffs. You can hand these to the child one at a time and sweep up any spills. You can also use a teaspoon to take tiny bits off the end of a banana or avocado and feed to baby.
I would not recommend feeding a reclining child anything but milk. Try laying down on the couch and eating a banana. Compare it to eating while sitting up. Eating while reclining is a choking hazard, at any age.
Also, keep in mind that when babies are newly exploring solids, they should be considered recreational eaters. That is, they're eating to explore new tastes and new textures, not for nutrition. The baby's primary nutrition comes from milk. It is just fine for to reserve solids for eating at home, and just feed the baby milk when out and about.
I never did formula, so I can't advise on that. I can say that the poop explosions will go down significantly, but don't presume they're gone!! :)
Water in a sippy cup is fine. For water in sippy cups, filling it full is usually easier for the baby, because they don't have to tilt the cup as much. (When they graduate to open cups, only put in half an inch or so, to minimize spillage.)
You can't overdo it on water. If the weather is hot/dry or you notice signs of dehydration, make sure you offer more water. Breastmilk self-adjusts to be more watery in hot weather, denser in cold weather. On formula, you may want to be more diligent about offering water.
If you really want/need to feed your baby with a spoon on a given occasion, we used the three-spoon method. Baby had one spoon in each hand, and the adult had a spoon. Adult would give the baby a bite of food. Baby would drop a spoon onto the high chair tray and grab the one in his/her mouth. Adult would pick up dropped spoon and fill it with food. Repeat the rotation of spoons until baby is done eating.
Hope this is useful. Congrats on your little one!