What's the most affordable way to file a complaint for an uncontested divorce? No assets involved.

The "most affordable way" and the "best way" are probably two different things. Many courts have forms for you to file yourself. However, they do not always have good resources for correctly completing these forms. The forms and issues can be much more complicated that they appear. Especially with custody, it is best to have a very strong agreement and judgment in place as your agreement with your husband may change later. It would be a good idea to start by getting an initial consult with a divorce lawyer for an hour or so just to get the idea of the lay of the land.

Based on the information that you have given, here is what needs to happen:
First, you need a written Settlement Agreement.
Since you apparently have children and they are not yet emancipated, that Agreement needs to cover custody and parenting time, as well as child support and other child-related financial issues.
If neither your husband or you has been paying alimony (spousal support) under the "status quo," and you both agree that there will be no alimony, that should also be stated in the Settlement Agreement. (The Settlement Agreement should give the facts which form the basis for the mutual waiver of alimony.
You say that "there are no assets involved." The Settlement Agreement should also confirm that, and each of you should represent that you have provided full disclosure to the other party about any assets.
You also say that "each party will assume debt in their name from this point on" and that "there is no joint debt." Both of those things should also be stated in the Settlement Agreement.
Once the Settlement Agreement is signed by both of you, the next step is for one of you to have a Divorce Complaint properly prepared, filed and served on the other party. In that Divorce Complaint, there should be a request that the Settlement Agreement be Incorporated into the Judgment of Divorce.
You ought to be able to get a date to "put through" the divorce on an uncontested basis in fairly short order after that.
Although you are not legally required to have a lawyer involved at any point in the process, I recommend that you at least meet with a very experienced lawyer who devotes his/her entire practice to New Jersey Divorce and Family Law matters.
Go over your situation in detail with the attorney, get educated answers to your questions, and obtain expert guidance. In my opinion, it will be well worth the cost of the meeting.

The most affordable way is to file the docs yourself. That is like performing brain surgery on yourself. You would not do that would you?
The next affordable way is go to a document preparer here they fill out the forms instead of you, and no legal advice is given. This is someone performing brain surgery on you with no medical training. You would not do that either would you?
THE BEST WAY PROTECT YOURSELF by contacting a local attorney, either by email or phone, who will protect you and your rights.
The best way to do this is by clicking on the find a lawyer tab on AVVO. Then find one that will offer you a free consultation. This benefits you in two ways, first and foremost you need to find an attorney who fits well with you and secondly to make sure that they are skilled enough to take on your case. The best case scenario is that you get your questions answered and you get a powerful attorney to help you if you need one.
Even though it is uncontested you want to know what you are doing is right, that way you both get exactly what you think you are getting. Do not go at this alone!

You can use the forms the court makes available. It would be best to have a settlement agreement to assist in handling the matter. You can do one on your own using online resources. However, you also can use the assistance of any attorney to facilitate the matter to a quick conclusion.

You see to be asking lawyers to tell you to do it yourself. I will not. You should at least consult with an attorney.

If the two of you are truly in agreement on everything, a family law attorney should be able to provide you (with only ONE of you as his or her client) with an affordable and timely procedure for drafting a marital Settlement Agreement and getting a Complaint for Divorce filed on behalf of one of you, then simply waiving answer, consenting ti default judgment, and appearing at an uncontested hearing where the agreement would be incorporated into the Final Judgment.

Provide for who pays for children's activities in what proportions, who decides what they are, how college will be paid for by the two of you.

I suggest that you schedule a consultation with a local divorce attorney. It might not be as expensive as you think. If there are few or no issues in dispute, the case can be settled quickly.
Good luck.

File pro Se then file application for Equitable distribution listing your agreements. That way you will only have to pay filing fee but not the answer fee which the defendant usually pays. If you both get along you can even split the filing fee.

Please consider consulting with an attorney. Many offer free consultations. There may be things you are not considering and it will only continue to lead you back to court time and time again if it is not done correctly.