You need to provide more detail. It is not possible to provide you with good information without you providing some detail.
This answer is not a substitute for consulting with and retaining the services of an attorney for your legal needs. By providing this answer, I am not entering into an attorney client relationship with you.
In some states, magistrate appeals can be heard in District court de novo. The first question would be are you trying to appeal a Federal magistrates order? As the others aptly stated, we need more info.
In addition to what has been said about magistrate's decisions, some types of agency decisions may also be instituted as trials de novo. (For example, a ruling by the U.S. Customs and Border Patrol on the tariff classification of an imported article may be challenged by a trial de novo). As others have suggested, the determinatin is highly case-specific.
I wonder why this question is of ineterst to you. If you're going to challenge a decision by a federal agency or a magistrate, a primary advantage (and also a danger, and an added expense) of a trial de novo, as distinguished from an administrative appeal, is this: facts that were not established at the agency may be introduced as evidence. And, of course, it is based on the evidence admitted at trial that the judge or jury makes its decision.
If on the other hand, you are asking a court for judicial review of an administrative decision, you are typically limited to the facts before the agency. In some cases that is quite advantageous. There may be evidence the agency would not have from its investigation, and you would not want them to have; you may not want to have to testify in a deposition or trial, which the government agency may compel you to do in a trial de novo. Discovery can be time-consuming and expensive and typically government attorneys have no where near the incentive to cut it off and enter into a settlement as does a litigant who is expending his own resources to litigate.
In an appeal, the court is reviewing the legal merits of the agency's ruling. To prevail, you generally have to show the agency's action was arbitrary and capricious or not based on substantial evidence. In general, in my experience, a trial de novo has the potential to be more costly than an administrative appeal from an agency decision, though, here again, that is ultimately dependent on the nature of the facts and the legal issues involved.
Finally, regardless of whether instituting a new trial or seeking judicial review, I would not try to represent myself in federal court. And I'm an attorney! There are invariably more pitfalls than you can imagine, certainly more than there should be, and the fail rate of pro se litigants is, I believe, tragically high.