Not having a trailer can be tricky, but in the end, I've managed to do just fine without one and know people that have gone even 10 years before they were ever able to get a trailer. I guess it all depends on the resources and people around you whether you'll need your own! I'm excited for this year as my boarder is letting me ride her horse along with mine and is happy to drive me to all the rides and crew for me so she can get out and have some horsey fun herself!
As for whether or not you need to condition on hills, I was passing on what the experienced head vet in my area said about trying to do endurance without doing at least somewhat regular hill conditioning. They don't need to be steep, but any hills help! Personally, I think I'll take the advice of my vet and make sure he's got at least decent hill work worked into his conditioning before I deem my horse race ready.
As for adding speed, a working trot (8-9mph) is best, and, per the "1000-mile or 2 years" philosophy, I wouldn't try to be fast or competitive until my horse reaches those marks. That's what ruins horses in this sport - something I've seen too many times at rides when a horse's life is put at risk simply because they wanted to "top ten". I don't push my horse at rides - I treat it like a really long conditioning ride with a lot of company.