All steroids are going to have side effects. The side effects are duration and dose dependent. Probably testosterone would have the least side effects. Any oral steroid, such as anavar or tbol is going to be very hard on your liver.
If you are concerned about side effects, your best option is going to be either SARMS or a natural testosterone booster such as HCGenerate from n2bm.com
http://needtobuildmuscle.com/store/Cycle-Support/-HCGenerate-p45.html
The SARMS triple stack would be a good first SARMS cycle to run:
http://www.evolutionary.org/the-SARMS-triple-stack-protocol
After the triple stack, run a mini PCT. 4 weeks of the following:
clomid at 25mg/day
nolvadex at 20mg/day
HCGenerate ES at 5 capsules/day
n2guard at 3 capsules/day
SARMS are minimally suppressive, there is no risk of aromatization (therefore no estrogen related side effects) and legal to use. You can get everything you need off sarms1.com, n2bm.com and ag-guys.com