Answer: Sorry to hear of your bad past sexual experiences, lack of sex education, and bad partners. It is wonderful that you are exploring your body and sexuality and seeking answers to your questions.
Your concerns about finding visual images of girl/girl sex and nude women sexually stimulating is a common concern among "heterosexual" women. If you read through the masturbation experiences visitors to the website have submitted, you will see several have had the same concern, but were happy to learn it is normal and common. I am not sure when such attractions and thoughts become an indication of sexual orientation versus when they are simply an expression of curiosity. In your case, it could also be because your male partners have been such poor lovers you are wondering if sex with another woman would be more fulfilling. For you to have a sexual relationship with a woman you should have a good emotional relationship with her first, your aversion to kissing a woman makes this unlikely unless you can figure out why this makes you uncomfortable.
I an glad to hear you have experienced your first orgasm. You may be trying too hard at this point and that is why you have not had another. If you try to have an orgasm it is much harder to have one. Relax and explore pleasure not orgasm. If it does not feel good, do not do it. Do not forget the importance of mental stimulation. Look at those sexy pictures while stimulating your clitoris. Spend the first half hour thinking about sex and looking at pictures, then start stimulating your body. While clitoral stimulation is very important, do not neglect the rest of your body. Limit your stimulation sessions to thirty minutes, or change technique and positions several times.
Buying sex toys depends on your needs. Vibrators come in many sizes and shapes, as you know. Quality and price are another concerns. The Hitachi Magic Wand is a very good and powerful vibrator that provides external clitoral stimulation. The large head stimulates a large area and a powerful motor drives it. I have bought them for several women who have enjoyed using them. They are often called the Cadillac of vibrators. They are a bit pricey at about $50 but will last ten or more years. The Pocket Rocket is battery powered yet powerful and is much smaller and costs around $20.
If you enjoy vaginal penetration and stimulation an insertable vibrator or a dildo may be desirable. I believe it is a matter of trial and error and what your needs are at the moment that determine what works best. A G-Spot vibrator may gain you nothing if you do not have a G-spot. You will likely find that you have a collection of insertables versus one that always fits your needs. You may want to buy one for yourself each Christmas and Birthday. Silicone dildos while more expensive are a better buy. You may have to experiment to determine which size or sizes is appropriate for you. You can experiment with vegetables first then buy the size you like. If you are open to and curious about anal stimulation a small and medium sized butt plug may be a good buy.
Since you enjoy visual stimulation and are learning to masturbate, I recommend getting a copy of Betty Dodson's video, Selfloving: Video Portrait of a Women's Sexuality Seminar would be a great buy. You can see other women masturbate and learn from them. You do not need to buy anything, there is tons of photos online in Yahoo Groups and other websites.