Hi Debra,
As Donald says, you've done an excellent job working out why and where you might need to improve and are tackling the whole thing with a logical approach. Without knowing the competition you might face, I hope you'll succeed.
I thought it might be helpful to provide a couple of thoughts on each in turn, so I numbered the shots in your post for ease of reference; one of the advantages of being a moderator
#1 - Great action shot of the dust kicked up, although with the inevitable/unavoidable hiding of the rider's face due to the nature of the event. The sun angle in relation to the horse's face has led to it being in shadow, whether a little dodging could reveal more detail in front of the eyes and forehead is unknown. Personally, I'd straighten this with a small counter-clockwise rotation, but not everyone would agree with me. The amount of foreground below the hooves and headroom above the rider 'feel' about right to me. If possible, I might have cropped a bit off the left hand side and added a bit on the right (
unless that brought in something heinous in the background).
#2 - Here the sun angle and shot timing has actually resulted in the cool effect of seeing the shadow of the horse on the barrel. The white spot in the horse's eye looks a little odd to me, not sure of the cause, may be natural (see also #6). This shot obviously addresses many of the issues raised with #1. I think #2 doesn't need this much foreground.
#3 - Definitely a shot in need of some dodging to reveal more detail in the shadows in key areas - or be shot from a different angle, or with a different sun angle. Feels a bit tightly cropped top and bottom, although I suspect you have done this to emphasise the speed. Perhaps needs a little more space on right to ride in to?
#4 - Again, some dodging to reveal the rider's face better would help, I feel. With regard to the background, this is noticeably softer than the others, although it is a different barrel and background I think), I wondered if you have had a go at this with a blur brush in PP? If so, while there, you might try a little cloning out and/or 'burning' of some irrelevant detail (e.g. hot spots) on some of the vehicles, for a better artistic shot, rather than 'documentary'.
#5 - The shadow on the drum is better here than #2.
Would benefit from dodging to reveal a bit more detail in the shadow areas. A tad tight at bottom, compared to top(?).
#6 - Would also benefit from dodging to reveal a bit more detail in the shadow areas. Don't need all that headroom(?) - perhaps a tad more on right(?).
As you say, a wider aperture, to achieve a narrower Depth of Field is the best way to go, I'd consider making that a priority a perhaps varying shutter speed and/or ISO to cope with small lighting variations next time.
Overall, the series has consistent exposure and White Balance, the only recurring issue, due to the harsh light on the day, is a lack of detail in shadows, which could be addressed (with practice) in seconds in ACR/PS.
In each shot above, I have been
ultra critiquey (not critical) to aid your already well developed thought processes, you should not accept everything I say as being correct/better though. I also got briefer in later images to save my typing time, that's all it is. Everything I said is open for discussion by you or other members.
In #4, I suggested some cloning, that comes with a caveat - the danger of cloning out stuff in a single shot (for artistic merit) is that across a series, if things are in the background of some shots and not others inexplicably, people may not trust your photos, so use cloning with caution, or not at all. Not to mention the time factor if this might be a commercial enterprise.
Thoughts for your next post here; it would be helpful for us to see larger shots (in order to assess technical quality better), so if you could upload ones that are at least twice this big in height and width, that would be great. My recommended maximums are; whatever the orientation 1000px height (max), thereafter, (if horizontal aspect, as these are) TinyPic will accept up to 1600 px width.
I note you're using PS CC 2014.
On memory card usage;
Were you shooting RAW + jpg? - If so, do you need to?
Or do you have a small size card? - Easily fixed
Or are you shooting too many in each burst (I do this!) - more experience will help here.
In summary, as a first attempt, these are very good.
Cheers, Dave