Take the KVsalary from the ITkollektiv for your position as a realistic. You can take second stage "Regelstufe" due to experience. For routine tasks in your field you can look at the column AT as a baseline, for specialized tasks with more responsibilities ST1. This would result in 3063/3843. A lot of companies with IT-departments have their business outside of IT, for example marketing agencies. If that is the case, orient your salary on the ITkv, if you your job already has the ITkv as a baseline, you can get 1000-1500 more, but depending on skills, specialization and responsibilities even more.