Which Hostas are good for beginners?
Almost all hostas are very easy for beginners to grow. There are many different color variations and sizes that are readily available at most local nurseries and on-line vendors.
For someone just starting out, the recommendation is mostly medium sized hostas, with a few smaller varieties and maybe one medium large if you have a bit of extra room. Too many of the minis are a bit touchier to grow initially, harder to find, and more expensive. The really large ones simply get too big for most newcomers--very few people realize how truly massive a Sum & Substance will be at maturity until they have seem one, and they are very unlikely to have the garden space to accomodate a plant that large until they have grown hostas for a few years and really caught the "fever". The average new hosta person has a shady border area between 2 to 3 feet wide, and needs to plan accordingly. As they get more involved they can dig up vast areas of their lawn and put that space to better use by filling it with hostas.
For specific plants the recommendation is the following based on reliable growth, easy of care (or tolerance of neglect), low initial cost, and wide availability. Golden Tiara, (or any of the other Tiaras), Gold Edger, Gold Drop, Pacific Blue Edger, Halcyon, fortunei Albo Picto, fortunei Aureo Marginata (often labeled simply as Gold Edge hosta), Golden Sceptor, Antioch, Moerheim, Green Gold, Honeybells, Royal Standard, Lancifolia, Minuteman, Patriot, Plantaginea, Krossa Regal, Sieboldiana Elegans, Shade Fanfare, Gold Standard, Crowned Imperial (the reverse of Gold Standard and a terrific plant), So Sweet, Undulatas of all types, Wide Brim, Striptease, Fried Bananas, Guacamole, Revolution, Ground Master, Allen P. McConnell, Abby, Ventricosa in all it's varieties, Candy Hearts, and August Moon.
All these are widely available, and any 5 or 10 selected from the list will make a fine collection. Simply pick the ones that appeal to you.
For those who find themselves immediately smitten with hostas, several additional recommendations follow. These are all fairly easy to find, slightly more expensive but still not outrageous, and all grow very well in a wide range of conditions. Some of them are also quite large or are minis, but all will grow well without special care. Tambourine, Polar Moon, Blue Angel, Blue Arrow, Blue Umbrella, Christmas Tree, Green Piecrust, Grey Piecrust, Fair Maiden, Little Aurora, Fragrant Bouquet, Fragrant Blue, Fragrant Gold, Geisha, Gold Regal, Regal Splendor, Sagae, Grand Master, Green Fountain, Inniswood, June, Stiletto, Invincible, Lemon Lime, Love Pat, Mildred Seaver, Montana Aureomarginata, Night Before Christmas, Nigrescens, Paul's Glory, Pineapple Poll, Pearl Lake, Blue Cadet, Sea Lotus Leaf, Spilt Milk, Sugar & Cream, Sum & Substance, Venusta, Yellow River, and Wolverine.
As you can see, the new hosta fancier can amass quite a large collection simply by getting reliable, easy to locate, moderately priced...