The best course of action for Trump is to support any and all investigations. Any counter investigation and impeding current investigation will only lead to him losing support and bringing about his impeachment.
He needs to focus on what he does as president, rather than comment that the left and the media are targeting him.
Anyone not totally married to the idea of the Russian collusion sees that it’s all a big nothing. Trump actions during the investigation are not meant to impede it and have more to do with him talking without thinking about the subtext of what he is saying, rather than part of any conspiracy. Even Jr. involvement, although made in bad faith and shows Jr. in a bad light does not constitute anything that can be leveled back at Trump.
After everything is said and done he could start investigating the investigators as to their true motives and finding those that pull the strings behind the conspiracy.