The short answer is you should be doing as many reload offers as you can!
The longer answer is that you should go to the reloads section on our website every day and look at what offers are time limited. Those are the ones you should prioritise for that day. When those are completed I would recommend having a look at the horse racing refund offers.
On quieter days you can then fill in any gaps with the weekly free bet clubs which should be the cornerstone of your reloads strategy as well as boosts.