I'm leaving the actual recipe up to you, just sharing my mock-smoking technique. If you really want input on the ingredients, I'd suggest mixing Sweet Baby Ray's bottle BBQ sauce, soy sauce, brown sugar, a drop of liquid smoke and a sprinkling of Chinese five-spice, all to taste.

Liberally mop over the ribs and wrap tightly in foil. Let it steep overnight in the fridge, then bake @ 250 for...quite a while. 3-4 hours. They won't overcook or get dry; ribs have lots of fat and connective tissue that you need the low-and-slow cooking to tenderize and dissolve. After they're done you can broil them to get a little color and crispness on the outside. It's more or less how I do mine; it's acceptable, if not really comparable to proper pit-smoking (would that I didn't live in a Manhattan studio, sigh).

I wanted to rub spices in, but didn't know for how long...

Do you put additional bbq sauce on after the overnight marinade?

So many recipes have you throw marinade away...should I just use and add more?

I go straight from the fridge to the oven with the tightly-wrapped package; you need to keep it sealed up during the cooking so everything will stay properly moist...if you bake the ribs "naked" you're going to end up with jerky. The moisture simulates the smoky self basting environment of a pit.

Generally you should toss marinades after using them, it's a food safety thing. If you boil it, you can use it as a sauce or ingredient though.

White sugar
brown sugar
salt
pepper
paprika
garlic flakes
onion salt
thyme

If you like spicy ribs, you could add cayenne or red pepper flakes.

I coat the ribs in the rub, wrap them in two thicknesses of tin foil and bake at 300 for two or more hours. Later, I take them out of the oven, discard the foil, brush on barbecue sauce (Sweet Baby Ray's hickory) and bake for about 1/2 hour in a 325 oven.

I do them longer at a lower temp (200), and use cumin, smoked paprika and some smoked salt in the rub.

Squeeze fresh lemon juice on them. Douse them with Worcestershire sauce.Then sprinkle with garlic powder and paprika. Bake at a low temperature for 2-3 hours The whole house will smell incredible and the ribs will be mouthwateringly good.

My smoker is an electric smoker which is basically an oven with the ability to also turn wood into smoke. So if you use the same temperatures and times, you should get similar results, but just without the application of wood smoke flavor. Although it won't be quite the same, you can always mix in a bit of liquid smoke into your sauce if you want some smoke flavor or you can just do without the smoke and your ribs will still be fine.

As far as rub and sauce goes, I suggest you just use commercial products until you get your method down and then experiment with your own recipes if you like. Most any supermarket is going to have a selection of commercial rubs. It's not that difficult to mix up your own spices, but I haven't found a bad commercial rub so it's not a bad way to go. I will sometimes use one or the other. My favorite commercial rub for ribs is Dizzy Dust which you can get from them or Amazon, or your local market may carry it as it's quite popular.

I usually make my own glaze, but commercial bbq sauce works great. Here's the recipe I use with the exception that I usually use cherry preserves instead of apricot.
http://smokintex.com/Recipes/Recipes_ApricotHoneyGlaze.html

As for pork ribs, I like to use St Louis style ribs which are nothing more than spareribs that have been trimmed by the butcher. If you can't get St Louis ribs, just go with regular spareribs. They are cheaper per pound than baby backs, so I recommend you hone your technique with them, but baby backs aren't really any more difficult.

The first step is to remove the silverskin. You may be able to get your butcher to do this for you, but chances are you'll have to do it. If you haven't ever done this you can get directions on the youtubes.

Next apply the rub generously and as the name suggests, rub it in.

First I cook my ribs directly on the rack in the smoker. While you can certainly wrap them in foil for the entire cooking time if you're doing it in the oven, I think it's better to cook them uncovered at first to render some of the fat off or otherwise you'll wind up with a fat soaked mess at the end. In the oven you can use a 1/2 sheet pan with a rack. Bake at 225F for 2.5 hours.

Next you'll be wrapping them in foil after applying your sauce. I like to use 3 layers as inevitably at least one layer will rip. Now how long you bake at this point depends on how you like your ribs. I like ribs that are gnaw off the bone, not fall off the bone. Many like the latter and this just entails cooking them longer, but if you do this, you probably won't be able to finish them on the grill as they will fall apart on you. I will bake them either in the oven or my smoker for an additional 3.5 hours in the foil at 225F (go for an additional hour for fall off the bone ribs). Then I will finish them on the grill at about 2-3 minutes per side until nicely caramelized, slice them, and serve with additional sauce if desired. Your cooking times may vary based on how many you are making and how hot your oven runs. For baby backs, cut your cook time by about 30 minutes.

Roast at 350 for about an hour and a half. Bill sauces them when he eats them.
And he buys both plain and pre-marinated, depending on what looks good.