Deca and Anavar are both good steroids to begin with, as they are some of the safest. Anavar is a great steroid, it's cyclic ester (lactone) in the A ring makes aromatization not possible, which is something that seems important to you as you do not want extra weight added by water retention due to estrogens. Athough Anavar is not a great androgen (an androgen by definition is a precursor to estrogen) it stimulates the formation of phosphocreatine and therefore ATP synthesis. This in turn helps athletes which need burst of energy and strength. Deca durabolin or Nandrolone on the other hand is a progestin, so it does not aromatize due to the the lack of methyl group at C10, so the aromatase enzyme can't be activated. Deca though does have the enone functional group, so it is not a DHT derivative like Anavar is. This means that the 5 alpha-reductase enzyme will affect the molecule, and deactivate it. Unfortunatly, since Deca is a progestin it will promote water retention and gynaecomastia, which is not something you want.
Anyways, the biggest downside to Deca is that due to it's popularity, test have been designed to detect it's use for a long time after its use.
Anavar is a safe steroid with short half life and will give you lean gains, while making you lose fat.
Deca will give you more gains as it is a better anabolic promoter as it actually binds quite strongly to the androgen receptor.