The first thing you need to do is get rid of that Springer and get a pointer of some kind!! Just kidding, of course. Those Springers are beautiful. I have a Llewellin Setter.
No one has ever accused me of not having an opinion, so I'll venture a little advice. You need something for primary tillage. An overlooked implement is a one-row or single shank subsoiler. That is a shank, or shaft, with a point on it that goes deep into the ground, 12 to 18 inches, and breaks up a hardpan. I subsoiled about an acre of ground Saturday that I intend to plant corn on next spring. Those subsoiler furrows cut into the soil allowing rainwater to go into the ground rather than running off or puddling. Another good implement, especially when used in conjunction with a subsoiler, is what we call a spring-tooth cultivator or a general purpose cultivator. This implement is much like a chisel plow, although it doesnt go nearly as deep. It is good for loosening up the soil in a garden or a field. You need a good disc harrow. This will cut up grass and crop litter on top of the soil, break up any clods that may be present, incorporate herbicide, and get rid of any emerging weeds that might come up between primary tillage and planting.
Then, you need something to actually plant the seed. Ideally, you should have a grain drill for the crops you mentioned. Grain drills are expensive, and a used one will probably require a good deal of maintainance. I have a drill, but most of the time I just spread my wheat, millet, even milo, with one of the conical "sling" type spreaders. There is a lot of discussion about the best way to cover grass seed or wheat seed, etc. A cultipacker is great, but most of the time, I just use my disc harrow set with the discs almost straight and only about two inches in the ground. A drag of some sort works well too. For crops planted in rows, such as garden vegetables or corn: If your garden isn't too big, one of the little Earthway seeders with a variety of plates is great. That's what I use. For planting corn patches over about 1/4 acre, I have a set of old planters that are of the type used around here 50-60 years ago for planting corn, cotton, peanuts, etc.
Tillers seem to be very popular with members here, and I'll agree that they are nice. However, I don't think they are a must-have item. I flat wore out a pretty good Landpride tiller that came with a tractor I bought. At the time, I was doing about 25 acres of intensive vegetable farming per year. I found that using the tiller that much was rough on it, and it required a good deal of maintainance. They do leave a good seed-bed, though.
So here's what I think you need: something for primary tillage, a subsoiler and spring tooth cultivator is what I like. A disc harrow. Something to put out seed and fertilizer, like one of the conical spreaders. A planter of some kind, like the Earthway. You said you have a bushhog, and other landscape type implements. There are a lot of other things, like a sprayer, a bottom plow, drag harrows, the list could go on and on. But you can get by with the items I mentioned.
Just another word about the subsoiler. I think one thing new farmers and gardeners overlook is primary tillage. They think if they harrow the ground up good and then run over it with a tiller, that it is in good shape. Unless your soil freezes down to about 16" every winter, it probably has a hardpan. That pan needs to be broken, and a subsoiler is about the only way to do it. It doesn't have to be subsoiled every year. Probably about every third year is sufficient. It will make a big difference in how your garden grows.