What topics do I need if I am only covering General level?

The Following are the minimum you need for the General Level. You will need to do a lot of practice with Problem solving ( solving complex problems by working things out , applying what you know to date and then  judging if your calculations are getting to help towards the solution before presenting the solution in a logical way).

Order of Operation
Estimating answers
Rounding to 1 decimal place
Numerical skills ( Whole numbes/Decimals/Fractions/Percentages
Integers
Adding/Subtacting/Multiplying of simple commonly used fractions and mixed numbers.
Integers ( positive and negative Numbers)
Integers and multiplications
Equivalent Fractions
Percentages ( with Calculator and without) of a quantity
Ratios
Speed Distance  Time
Index Notation
Scientific Notation
Money & Simple Interest
Expenditure/  Borrowing/Discounting & VAT
Units: Length, Mass, Volume
Tolerance
Shape : Naming Angles
Types of Angles
Triangles
Quadrilaterals
Polygons
Circles & Tangents
Angles and Arcs
3D Shapes
Coordinates and straight lines
Symmetry
Pythagoras
Distance Formula
Scale Drawings
Enlargement & Similarity
Right Angle Triangle
SOHCAHTOA
Gradients/Depressions/Elavations
Trig Graphs
Sine and Cosine Rule
Area of  a triangle
Bearings
Basic Algebra
Multiplying out brackets
Squaring Brackets
Factorising( Common factors/difference of 2 squares/pairs of brackets)
Multiplying and Dividing Algebraic Fractions
Adding and Subtracting Algebraic fractions
linear equations ( eg x+40 = 4x -20) 
Quadratic Equations
Solve simple Linear Equations ( eg 2x-6 <10 )
Solve simultaneous Equations by graph and by elimination or substitution)
Changing Subject of formula
Realtionships and patterns
Indices
Graphs of Functions
Quadratic and Linear Functions
Sketching Quadratics
Finding the eqaution of a function
Proportions ( Inverse & Direct)
Direct and indirect  Variations
Statistics : Mean ( average) /Median/Mode/Range
Frequency Tables
Quartile & Semi Interquartile ranges
Standard Deviation
Graphs & Charts : Bar Chart/Line Graph/Pie Chart
Stem & Leaf diagram
Dotplot
Boxplot
Scattergraph
Pie Chart and its construction
Identify trends in Graphs'
Best Fit line in Scatter graph
Probabality
Relative frequency and probability.