I’m happy to help.

Yes there are more than 300 functions.

Most Fundamental (in my opinion):
IF, COUNT, COUNTA
SUM, SUMPRODUCT
COUNTIF(S), SUMIF(S)
AVERAGE, AVERAGEIF(S)
MAX, MIN, ROUND,
INT, ABS

Second tier (in my opinion):
MATCH, INDEX, ROW,
COLUMN, ROWS, COLUMNS
AND, OR, NOT
IFERROR, ISNUMBER