I have a plan to go first to Bulgaria, then visit some Schengen countries (Hungary, France – Spain). From 2015[update], Andorra, Monaco and San Marino negotiated an association agreement with the EU. Andorra`s ambassador to Spain, Jaume Gaytén, said he hoped the agreement would include provisions that would make states associated with the Schengen agreement.  With the entry into force on 1 May 1999 of the Schengen Protocol to the Treaty of Amsterdam of 2 October 1997, Schengen cooperation was transposed into EU law, initially solely on the basis of an international agreement. Since June 2017, ten urban transport agreements have come into force. Schengen states that share a common land border with a third state are allowed, in accordance with the European Union Regulation 1931/2006, to conclude or maintain bilateral agreements with neighbouring third countries for the purpose of implementing a border area system.  Such agreements define a border area of up to 50 km on both sides of the border and provide for the granting of permits for small border traffic for the inhabitants of the border area. Authorizations can be used to cross the EU`s external border within the border area, are not stamped when crossing the border and must include the name and photo of the holder, as well as a statement indicating that the holder is not allowed to travel outside the border area and that any abuse is punishable. At many external border crossing points, there are special routes for EU, EEA and Swiss citizens (as well as family members) and other routes for all travellers, regardless of nationality.
 At some border crossing points at the external border, there is a third route for Schedule II travellers (i.e. third-country/EEA/Swiss nationals who are exempt from the visa requirement).  Although Andorran and San Marines citizens are not EU or EEA citizens, they may use special routes for EU, EEA and Swiss citizens.  British citizens will not be able to use the EU`s trace after Brexit under current rules, unless such a right is introduced into the Brexit deal with the EU. I saw online that one can visit Bulgaria with a valid Schengen visa. Does this mean that you should have a valid schengen land visit before visiting Bulgaria or I can visit Bulgaria directly with only Schengen visas and then visit other Schengen countries. Visa liberalisation negotiations between the EU and the Western Balkans (excluding Kosovo) began in the first half of 2008 and ended in 2009 (for Montenegro, Northern Macedonia and Serbia) and 2010 (for Albania and Bosnia and Herzegovina). Prior to the total abolition of visas, the countries of the Western Balkans (Albania, Bosnia and Herzegovina, Montenegro, Northern Macedonia and Serbia) had signed “visa easing agreements” with the Schengen states in 2008. Visa facilitation agreements should, at the time, reduce wait times, reduce visa fees (including free visas for certain categories of travellers) and reduce red tape.
In practice, however, the new procedures have proven to be longer, heavier and more costly, and many have complained about the ease of obtaining visas before mediation agreements come into force.    Authorizations are issued for a period of one to five years and allow you to stay in the border area for up to three months. Permissions may only be granted to legitimate residents of the border area who have been in the border area for at least one year (or more if provided for in the bilateral agreement). Applicants must prove that they have legitimate reasons for frequently crossing a land border under the local border transportation system.