I would like to mention few things which will help you designing your own wordpress theme . Its easy to design wordpress theme if you have already designed lots of sites . Just you need to know how dynamic php scripts work and how to interconnect different pages with the database . The main thing which contribute to your theme overall is the layout of your designed theme , if it will be having a good appeal then everyone would like your theme otherwise it will look odd  .

Graphic designing work is very important in designing any theme , due to the graphical work your theme blend . Most of the people on web like theme which is having a good graphical work & very less number of people search for quality written themes . For me both things are necessary as limitation of one thing will divert your visitors attraction .

I have designed lots of wordpress themes and I have noticed that good graphical work bring more customers as compared to the ordinary graphical work with good scripting . Good scripting might help you in bringing more traffic from the search engines yet good graphical work is liked everywhere .

Although lots of people use bloggers as well yet wordpress is the standard for self hosted blogs , if you want to host your blog with bloggers then blogspot is the best option . I hope it would help !