Create Campaigns, set bids and buy adds from DoubleClick Bid Manager API
I found the way to solve this problem. The actual API v1 has this capabilities but the documentation is not very clear about it.
You need to download your Line Items file as CSV or any other supported format, then from that downloaded file you must edit it with any script you want, so you must edit the columns of Status to perform this operation. Also, if you want to create a new campaign, you will need to do the same for new Line Items. After editing the CSV or created one, you must uploaded back to google with the relative endpoint: uploadlineitems.
Google will answer to the owner of the Bid Manager account what changes were accepted from that file that you sent. 
I have confirmed that this is the same behaviour that Google uses for other products where they consume their own API:

Download or Create Line Items file as CSV or any other supported format.
Edit Line Items.
Upload Line Items.

So basically you only need to create a script that edits CSV files and another to authenticate with the API.
Is it possible with the Google DoubleClick Bid Manager API to create campaigns, set bids and buy adds?, I have checked the documentation and it seems that there are limited endpoints. 
These are all the available endpoints according to the documentation:

doubleclickbidmanager.lineitems.downloadlineitems    Retrieves line items in CSV format.
doubleclickbidmanager.lineitems.uploadlineitems  Uploads line items in
CSV format.
doubleclickbidmanager.queries.createquery    Creates a query.
doubleclickbidmanager.queries.deletequery    Deletes a stored query as
well as the associated stored reports.
doubleclickbidmanager.queries.getquery   Retrieves a stored query.
doubleclickbidmanager.queries.listqueries    Retrieves stored queries.
doubleclickbidmanager.queries.runquery   Runs a stored query to
generate a report.
doubleclickbidmanager.reports.listreports    Retrieves stored reports.
doubleclickbidmanager.sdf.download   Retrieves entities in SDF format.

None of these endpoints can do tasks as buy ads, set bids or create campaigns, so I think those tasks can only be done through the UI and not with the API.
Thanks in advance for your help.