There are many things to consider before ordering plants. If you order them and figure out what to do with them they arrive, it could absolutely work out, but having done this many times myself I can say that some preparation and planning will dramatically improve your results!
Site selection, preparation, and maintenance are the most important aspects of growing plants. If you plant a cactus in a low wet area, or an elderberry on a dry rocky ridge, get ready for disappointment. But there are so many plants and so many soil types and climates! This is the beauty and mystery of a life-long education in growing plants. The most general guidelines that will almost always be of help are the following:
Weed. Remove other plants from the area where you want your plant to grow. If there is sod, sheet mulch it ideally for at least a couple months if not a year before you plant there. Or use a fork or shovel to break up the sod, remove as many roots as possible, and then sheet mulch it. Removing roots of perennial weeds, adding compost, sheet mulching, and covering with wood chips is about as good as site preparation as is needed to grow most plants. Spending the time to thoroughly remove roots of perennial weeds will be well worth it in the long run.
Loosen the soil. Using a broad fork, a shovel, a tiller, or a tractor mounted implement will allow for easier removal of weeds and generally makes shaping the bed easier. If you simply dig a hole and plant a tree, the tree will probably grow but if it has more loose soil free of weeds to spread its roots into it will grow much faster and provide you with fruit sooner.
Provide fertility. If you have specific concerns, you can do a soil test to find out what your levels of important nutrients are. If that doesn’t sound like a lot of fun to you, you can work on understanding soils from an intuitive level to great effect. Darker soil generally means more organic matter for example. Hard dry light colored soils may benefit greatly from the addition of compost or some form of organic matter. Dark mucky and wet soils may benefit from increased drainage. Any sort of manures, composts, compost teas, liquid fish fertilizer, biodymanic preps, or other additions that you may want to do will certainly help your plants, but don’t discount the simplicity of the three macro nutrients, Nitrogen, Phosphorus, and Potassium. There is a good reason why farmers are always so focused on NPK, because usually poor plant growth is a result of low levels of one or more of them. There are many natural ways to increase the levels of these nutrients with urine, phosphate rock, and potassium sulfate or langbeinite. Azomite is a broad spectrum micro nutrient mineral that can also help out, but a little goes a long way.
If you can make a nice big bed with 9” of loose soil, mounded up to provide good drainage, with added compost, free of perennial weeds, and covered with a nice layer of mulch, you are ready to start planting! Maybe your first bed gets filled with so many plants that there’s no room for them. In that case, let your bed become a nursery bed. Plant your trees and shrubs in the well prepared nursery bed, and during that season prepare other areas where those trees really want to be located for the long term. Then at the end of the year once they are fully dormant, dig them out and replant them.
It is wise to always have well prepared empty bed space on hand in spring when the compelling desire to bring more new plants into your life overwhelms all reason and logic with dreams of fruit, flowers, and lush verdant growth.