When I started learning Czech on Memrise I just plumped for the first course on the top of the list. After a week or so I found the length of the course I'd chosen dispiriting as it never seemed to come to an end. I then looked down the list and picked out courses with the fewest amount of words. I've found these suit me best, as I get a sense of achievement when I can harvest words and finish a course within (to me) a reasonable amount of time. This may say more about me than the courses and is not meant as a criticism, just a comment.
I have found Memrise a huge help in my Czech learning and thanks to you both, Doralina and Mangodurian, for all the work you’ve put in.