Short term memory and an effective learning strategy
By one of Tony Buzone's memory book, I would say the right way is to memorize a topic/data, then do a 10 minute break. After 10 minutes, repeat it again. Then, Repeat it the next day, the next month and then the next half a year. That should put the topic in your memory in the long term.

However, it also depends on what kind of data there is in each topic. If the data is too similar with each topic, it will be too hard to memorize all topics at once without being confused and without mixing up facts. Other factors that you didnt mention are the volume of material in each topic.

Lastly, order of topics is not important. You may reverse the order of the topics to devote your mental effort to the hardest topic as being hte first...