The first thing to consider is how much land do you have and where is it located? No matter where you are, there are laws that apply to disposal of both gray water and black water (human waste). Since you say that you don't own a truck to tow it with, I'll assume that you are or plan to live in it as a fixed home?
No matter what you don't want to dump either on the surface near your RV because it will create a stinking mess for you very quickly. If you are remote enough and have a large property you might be able to get away with digging a hole to dump into but that will soon smell awful and if anything drains on to neighboring property, even when raining you will soon have legal issues. If you contact a septic service they can give you a price to come pump out your tanks but that will probably cost somewhere between $70 and $200 per trip, depending on where you are located. To haul the waste yourself you will need to install a macerator pump on the RV that will pump it up and into the tank that you use and you will probably have to pay someone to allow you to empty the portable tank. If you are considering putting in a septic system, the cost ranges from $3,600 to $10,000 with an average cost for septic tank installation is about $6,500. That too will depend on where you are but you should be able to get some quotes pretty easily. In the long term it would be the best answer.