Without in. 'Towards' and 'in' are both prepositions, you should only use one.

Hello Niwantha, First I will correct then i will explain. "I have set a few simple targets for myself and I am so looking forward to working on achieving them." OR "I have set a few simple targets for myself and I am so looking forward to working on achieving them." First, i got rid of "to working towards" because it was unnecessary and makes the sentence more complicated than needs to be. You already wrote that you were looking forward to something, so saying" looking forward to working towards" is redundant and repetitive. Using forward as an adverb already implies that is toward a place or time beyond. Second, achieving and working are gerunds (verb+ing), and here they are used as a nouns. It is answering the question what?, What are you looking forward to? I look forward to working on achieving goals OR i'm looking forward to working on achieving goals. You do not need the "in" after the verb "achieving", you achieve goals or you look forward to achieving goals, you do not "look forward in achieving goals". I hope it helped! Let me know if you need me to further explain