1. The most important thing is good soil. How large an area are you talking about? Generally, I would not add top soil. I would improve the existing soil by adding organic matter - compost, composted cow manure, etc. If the area is not too big, you can buy it by the bag in garden centers or some towns have recycling centers where you can get it for free. Dig this stuff in and mix it as best you can. The first time I tried to garden, I just dug a hole and stuck a plant in. Nothing happened. So you learn real quick about soil.
2. Need more info to recommend plants. Is it sunny or shady site? Do you want annuals or perennials or shrubs? But more important, what do you like/want? It's up to you. Look around a garden center and see what appeals to you. And have fun!

Hello, Guest- Welcome to GW.

1. Please take the time to read through the various postings on this forum. You will find opinions on the type of soil (including the oft-recommended lasagna method of making your own soil!) and on various ways of making new beds for flowers or vegetables. You can also use the 'search' feature at the bottom to look up specific subjects -- try 'lasagna' or 'new bed' to see what I mean: the search-engine will bring up each posting that contains the word or short phrase requested. Also, you could "lurk" [read the various threads] in forums like those on "soil" or for specific plants such as roses or a particular type of garden, such as cottage or vegetable.

2. I don't think anyone is going to suggest what you should grow! We may post ideas to meet a specific situation (shade or fragrance or height, etc.) but those ideas will take into consideration your planting zone, soil, shade, preferred plant size/type, and area available to plant as well as your potential skill. You mention being new, but all the other info is lacking so we don't have any guidelines.

Agree with the above....but would like to add that potting soil is best used in pots and not added to a garden.
Regardless of what kind of soil you have, compost is the best additive.
Linda C