My goodness I would have never survived if I had kept feeding my boys every three hours at 5 months! Once the boys were over 12 pounds we went to feeding 6 times/day - about every 4 hours. Usually it was a six ounce bottle, but 4 oz if they had another bottle within the 3 hours prior. Since your daughter has acid reflux, I would stick with the frequent small meals so she's not as uncomfortable.
To get started in a routine, first we tried doing different things at different times and kept a mental note of what things we did on a GOOD day. Then we did that again to see if it still was a good day. It took some time and I don't think we had a routine down until they were 8-9 months, if not older, maybe even 11. That was because we would let them sleep whenever they seemed tired, not when it was nap time, and that kinda through a kink into things. One thing we did do to try and get our boys to go to bed at the same time was make everything in the same order from dinner time on.
I remember everyone being so hard core about getting on a routine asap, but it felt horrible to me to say, "ok, now we eat, now we play, now I change your diaper, and oh it looks like your sleepy so lets take a nap." But really, I don't think it's a huge thing to stress over the first year, especially if you haven't been moving all over the place or switching daycares every couple of months.
Anyways, we didn't start with solids or cereal until 6 months. So at 5 months the "routine" was wake up, new diaper, bottle, go back to sleep (some days they woke up at 3:30, and there was no way they were playing), later, eat again (7-8ish) play with rattles, swing, play in exersaucer, etc... all for a couple hours, then nap for 2-3 hours. Wake up, have lunch, then in the afternoons we worked on whatever skill the baby books said they could or should be able to do by the next month. If they were sick, we usually cuddled up with Baby Einstein - even though we're not suppose to. Then nap again for about 2 hours, eat again, read books and/or play until dinner time, which came at 4 or 5ish. Usually after eating we would let them play in the exersaucer, or some activity where we had some freedom to clean up the days' messes, including another small nap if they were tired or overly fussy. Then about an hour before bed time, we did baths and lotion, looked at a couple books (taking 15 minutes or less), gave then their last bottle - usually about 8 ounces at night, then put them to bed @ 8 or 8:30!
They were sleeping through the night beginning right at 5 months - and that meant they slept about 6-8 hours straight depending on the night.
The thing is, I've "heard" that kids with acid reflux are really challenging the first year. If this is the case with your daughter, I wouldn't worry so much about what your suppose to do and just focus on meeting her needs and milestones to get through the first year. Obviously, let your ped know what you ARE doing at the 6 month check up so that he/she can let you know if your making committing any major offenses. Sleeping and eating patterns may be different for your child because eating too much makes her tummy hurt and acid reflux in general makes sleeping for extended periods of time difficult since you can't "stuff" them full of food before hand. What we did was focus on reading our babies cues. By 11 months they were toothlessly taking cereal, playing, throwing tantrums or screaming, crawling and destroying our house. That was when we finally became determined to make sure to follow the rules and suggestions about routines.