Hello, I have more than 2 years experience, I created one of best RolePlay gamemode's in the world with more than one year working on it, also I created many other RolePlay & DeathMatch gamemodes.
Also, before I stopped with SAMP scripting, I was one of best balkanian SAMP (pawn) developers.
Unfortunately your budget is not big for creating GameMode script from zero, because for it its huge time needed.
I can edit for you one my old project, translate it to english, convert it to MySQL and optimize it maximaly.
That old project is also one best GameModes also its 100% dynamic, with including most quality samp maps.
GameMode is dynamic, so you can create all InGame, etc. Cars, Houses, Organizations.
After that editing, I can do changes what you want, any system what you want I will create it for you.